Well I originally posted in the general theater forum for some ideas for some curtains and such, but I have now decided to go all out with acoustic treatments, paint, columns, crown mold, etc. (how the heck did buying a ceiling mount for my projector turn into this?!?!?)
The room is 15W x 18L to the back closets (see pics below), with a another 3 foot walk between the closets to the doors Ceiling is 10' tall at the high point.
Here is my current equipment, all this is random stuff I have accumulated over the years and I don't plan on upgrading anything to soon do to cost (next on the list to upgrade is the projector):
Denon 3805 reciever
Klipsch KSP 300 Towers
Klipsch SW10 Subwoofer
Old Snell THX Certified Center Channel (hand me down)
Harmon Kardon Surrounds (from previous owner)
ViewSonic PJ1200 (not to bad actually considering its age...I was suprised)
Xbox 360 for DVD's and games
Here is the old setup with a 75" 4:3 screen (left by previous owner):
Update: Here is the room in its current (finished for now...) state:
First order of business that I did last week:
-Built a 110" BOC Screen following some of the guides in the DIY Screen Forum. I used the 2-frame method for the border, which actually turned out to be a bit of pain getting it to align correctly after all the fabric was on. I used Joan's BOC and black velvetine (was $30 instead of $16 for felt but looks 10x better, real velvet was twice as much as the velvetine!)
-Rerouted the wiring for the equipment to a back closet instead of under the screen. Bought 170' of 16 gauge 2-conductor wire (shielded/fire proof stuff used to pre-wire houses) and 35' of coax to route everything to the back closet. Luckily there is a attic/storage space on either side of the room, so running the wire was easy enough. I also bought the terk leapfrog system for $50 so all my remotes will work and it works great (just need to make the transmitter more stealth). Now just have to cover the wires on the front wall which is a 2nd floor exterior masonry wall (more on this below). I still need to zip tie and make everything tidy in the attic space:
-Mounted the center channel above the screen in the below pic, I have now decided to mount it below the screen so it is more level with the towers.
-Ceiling Mounted the Projector 19 feet back from the screen. This distance lines up with the back closet. I cut a hole in the top of the closet to get above the ceiling to run the wires without tearing up the sheet rock in the room. Works great with a pretty decent picture for an older projector.
-Blacked out the windows using black trashbags
Here is what it looks like so far:
Front:
Back:
I have ordered black velvet curtains for either side of the screen (walmart ones for $10 each).
Now the fun part, I plan on ironing out the design this week and next and starting on the construction within a couple weeks.
I will build a "stage" that will block the wires and such on that front wall as well as providing a stand for my center channel. There will also be a channel for purple rope light (shining down) at the top of the wall part (right below the screen border). I also plan to do the rope light behind the screen up on top. The stage will probably be covered in black faux suede but will light up purplish from the rope lights:
I plan to build crown molding at the top of the walls where it meets the angle. I haven't completely got the design worked out yet, but I think the simplest method is to bolt a 1x1 to the studs, then nail a 1x4 into that (from underneath), then attach the crown molding to the 1x4. Additional support will be provided by the columns. This will also provide an area for rope lighting (I plan on using purple rope lights on a dimmer).
I plan to make the columns fairly simple, using 1x4's for the sides and a 1/4" sheet on the front, then just make a rectangle out of trim. One long rectangle I think will look best due to the short height - it should help make the columns seem taller. Some trim around the top would look nice, but would require that the crown mold tray stick out further, and given the low height I don't want people to see the rope lighting inside (its only 6.5 feet high) I will mount these to the wall putting a 2x4 on the inside back of the column, then drilling into that from behind the wall. This way I can remove them later for whatever reason, and the mount is completely hidden (remember there is dead attic space behind these walls, so I can just add a 2x4 between the studs wherever the columns are).
Using 2 columns 9 inches wide on each wall will leave 53" spaces between them. This was key due to fabric primarily coming in 54" widths, as this will leave me enough room to staple the fabric on the sides of the frames. I haven't decided exactly how to do the acoustic treatments - 1" 703 fiberglass would be great but I'm hoping I can find something thats 3/4" thick instead so I don't have to do any goofy sizing (it will be much easier to just use 1 x whatever rather than having to rip boards down to 1 inch thick for the fabric frames). I haven't decided on fabric, but I think a purple faux suede or something would be really cool.
As far as colors, I am searching for a dark purple fabric to use on the stage and sidewalls. The Columns/crown mold/doors/trim will all be repainted a satin black (flat black is to much of a hassle in these high touch areas). I plan to paint the ceiling and above the screenwall area flat black. I will probably higher a painter for this part due to how much I hate painting ceilings and the difficulty in using flat black without roller marks. I'll repaint the back walls around all those doors a satin black as well most likely. One other note, the fabric frames will only go back to those side doors to the attic spaces, which is where the 177" total length comes from as far as column spacing. I'll just paint that last area black. The shading differences in the blacks in the pics is just to show the detail, it will all be the same color in the actual theater.
Eventually I will recarpet, but for now I'm hoping to end up with something that looks a little like this:
Other thoughts:
Possibly mount the side speakers in the rear columns, as their current position behind the listener and up high is not ideal.
Possibly still use sconces between the columns. My current sconces are on a dimmer switch and I am thinking about using their wiring for my rope lights.
I'm still working out the best/simplest construction method for everything as I have never tried to build columns or crown mold before (the crown should not be too hard since im not "turning" it where i have to figure out crazy double 45 degree angles lol!)
The room is 15W x 18L to the back closets (see pics below), with a another 3 foot walk between the closets to the doors Ceiling is 10' tall at the high point.
Here is my current equipment, all this is random stuff I have accumulated over the years and I don't plan on upgrading anything to soon do to cost (next on the list to upgrade is the projector):
Denon 3805 reciever
Klipsch KSP 300 Towers
Klipsch SW10 Subwoofer
Old Snell THX Certified Center Channel (hand me down)
Harmon Kardon Surrounds (from previous owner)
ViewSonic PJ1200 (not to bad actually considering its age...I was suprised)
Xbox 360 for DVD's and games
Here is the old setup with a 75" 4:3 screen (left by previous owner):

Update: Here is the room in its current (finished for now...) state:
First order of business that I did last week:
-Built a 110" BOC Screen following some of the guides in the DIY Screen Forum. I used the 2-frame method for the border, which actually turned out to be a bit of pain getting it to align correctly after all the fabric was on. I used Joan's BOC and black velvetine (was $30 instead of $16 for felt but looks 10x better, real velvet was twice as much as the velvetine!)
-Rerouted the wiring for the equipment to a back closet instead of under the screen. Bought 170' of 16 gauge 2-conductor wire (shielded/fire proof stuff used to pre-wire houses) and 35' of coax to route everything to the back closet. Luckily there is a attic/storage space on either side of the room, so running the wire was easy enough. I also bought the terk leapfrog system for $50 so all my remotes will work and it works great (just need to make the transmitter more stealth). Now just have to cover the wires on the front wall which is a 2nd floor exterior masonry wall (more on this below). I still need to zip tie and make everything tidy in the attic space:

-Mounted the center channel above the screen in the below pic, I have now decided to mount it below the screen so it is more level with the towers.
-Ceiling Mounted the Projector 19 feet back from the screen. This distance lines up with the back closet. I cut a hole in the top of the closet to get above the ceiling to run the wires without tearing up the sheet rock in the room. Works great with a pretty decent picture for an older projector.
-Blacked out the windows using black trashbags

Here is what it looks like so far:
Front:

Back:

I have ordered black velvet curtains for either side of the screen (walmart ones for $10 each).
Now the fun part, I plan on ironing out the design this week and next and starting on the construction within a couple weeks.
I will build a "stage" that will block the wires and such on that front wall as well as providing a stand for my center channel. There will also be a channel for purple rope light (shining down) at the top of the wall part (right below the screen border). I also plan to do the rope light behind the screen up on top. The stage will probably be covered in black faux suede but will light up purplish from the rope lights:

I plan to build crown molding at the top of the walls where it meets the angle. I haven't completely got the design worked out yet, but I think the simplest method is to bolt a 1x1 to the studs, then nail a 1x4 into that (from underneath), then attach the crown molding to the 1x4. Additional support will be provided by the columns. This will also provide an area for rope lighting (I plan on using purple rope lights on a dimmer).

I plan to make the columns fairly simple, using 1x4's for the sides and a 1/4" sheet on the front, then just make a rectangle out of trim. One long rectangle I think will look best due to the short height - it should help make the columns seem taller. Some trim around the top would look nice, but would require that the crown mold tray stick out further, and given the low height I don't want people to see the rope lighting inside (its only 6.5 feet high) I will mount these to the wall putting a 2x4 on the inside back of the column, then drilling into that from behind the wall. This way I can remove them later for whatever reason, and the mount is completely hidden (remember there is dead attic space behind these walls, so I can just add a 2x4 between the studs wherever the columns are).

Using 2 columns 9 inches wide on each wall will leave 53" spaces between them. This was key due to fabric primarily coming in 54" widths, as this will leave me enough room to staple the fabric on the sides of the frames. I haven't decided exactly how to do the acoustic treatments - 1" 703 fiberglass would be great but I'm hoping I can find something thats 3/4" thick instead so I don't have to do any goofy sizing (it will be much easier to just use 1 x whatever rather than having to rip boards down to 1 inch thick for the fabric frames). I haven't decided on fabric, but I think a purple faux suede or something would be really cool.

As far as colors, I am searching for a dark purple fabric to use on the stage and sidewalls. The Columns/crown mold/doors/trim will all be repainted a satin black (flat black is to much of a hassle in these high touch areas). I plan to paint the ceiling and above the screenwall area flat black. I will probably higher a painter for this part due to how much I hate painting ceilings and the difficulty in using flat black without roller marks. I'll repaint the back walls around all those doors a satin black as well most likely. One other note, the fabric frames will only go back to those side doors to the attic spaces, which is where the 177" total length comes from as far as column spacing. I'll just paint that last area black. The shading differences in the blacks in the pics is just to show the detail, it will all be the same color in the actual theater.
Eventually I will recarpet, but for now I'm hoping to end up with something that looks a little like this:

Other thoughts:
Possibly mount the side speakers in the rear columns, as their current position behind the listener and up high is not ideal.
Possibly still use sconces between the columns. My current sconces are on a dimmer switch and I am thinking about using their wiring for my rope lights.
I'm still working out the best/simplest construction method for everything as I have never tried to build columns or crown mold before (the crown should not be too hard since im not "turning" it where i have to figure out crazy double 45 degree angles lol!)