Well I certainly understand budget constraints and the like. I am more than willing to chime in and give you my two cents. It would help though for you to tell us what you were looking for or give us ideas on what your plans were and ask for guidance based on those plans, but since you have basically just asked for our opinions I'll give you mine. 8-) So here goes.
First you took a space in your home and turned it into a home theater. That is awesome, as most people don't even have the vision to do that.
As you know the space is not ideal but there are several things you can do to improve things that are free or at least a lot cheaper than gutting it and starting for scratch.
1) Declutter, clean up, and for the screen wall remove anything that is distracting. IMO I like a decluttered screen wall. Speakers and screen that is it. Nice clean look.
2) Give you walls a fresh coat of paint, you don't need to go bat cave here. A nice darker shade of blue, green, red, or brown will freshen up the space and give a nicer look than the acres of paneling.
3) Paint that bright white ceiling, this would be ok to paint in black, but you also could go a darker color of the color you pick for the walls.
4) Build a riser for the rear set of seats.
5) If you have a HTPC use it! Hook that bad boy up!
6) Move or as you have indicated build a A/V rack to neatly hold your equipment preferably to the side or rear of your space.
7) Buy plastic channel or modify your baseboards so you can run and hide your wires, so again you have a nice clean look.
8) Buy some window coverings (drapes) for your windows to help dress up the space. It is ok to bring the wife in on this. More than likely she is better at that type of stuff than you are. Or at least that is how it works in my house
9) You may not have the money now, but you will eventually so draw up some plans for the future to have some goals to work towards. This could include just about everything from layout, to furniture, and equipment.
10) Check out the some of the threads here that the OP's have done amazing things on a very limited budget and learn from them.
11) Finally......Get rid of that MAX PAYNE poster! J/K of course.
Good luck and I hope this is what you are looking for.