Cool theater! I found it interesting as my room is the same dimensions except with a higher ceiling: 18' x 10.5' x 8'. My room actually used to be the garage, you can check out my thread here
. I did mine the traditional long way and fit a 114.5" (diagonal) screen. I have two rows of seating which fits 6-8 comfortably, though some of the seats are too close to the surrounds. I already owned ALL the equipment, including the screen and furniture. I did my room for ~$4000, which was ~$1500 for materials and ~$3500 for labor. I hired a friend of the family @ $30/hr for a lot of it, but also did a lot myself.
I never thought to use the room the short way! I already owned the screen, so I couldn't go with a smaller screen, and the door is in the middle of the 18' wall.
Your seats look awesome! Is the brightness uniform from the wings?
Definitely paint the ceiling and front wall black. My room is also textured (sprayed with gobs of drywall mud), which is actually better since the rough surface scatters the light. Your ceiling looks like a knock down texture? (That is where they spray with gobs of mud, then smush the gobs with a drywall knife.) If so, I imagine the effect is similar and it will look great black. I posted an awesome flat black paint to use in my thread, though it marks if touched. Besides improving contrast by reducing reflections, the black ceiling makes the room seem bigger, probably great for you since you have 7' ceilings.