I was looking at getting a fabric to put on the projected wall behind the screen so that the screen stood out more. I figure if everything in your view is black, other than the screen, you will only focus on the screen and not try to compare it to anything else in view. I was hoping to find some black light absorbing fabric that would be cheap (temporary) and possibly that I could get at the local Jo-ann's Fabrics. Once I get my reflector polished, the black fabric up, and possibly get a Black Flame Lite Mix going, I should be set for finishing off the box. I've heard the black fabric a photographer would use for a background is best because they use it for absorbing light, but I have no idea what it is called.

black felt

I got these back curtains from WM for $20 @, they do have a little sheen to them, but not bad and it helps me acheive that effect your talking about...

While not quite as easily available as black felt.. I used this material as the boarder on a screen I made..
I found it here
not sure if this is the best price for duvetyne (comando cloth). but i do know it did a great job... I was using a panasonic AE100 at the time, and you could hardly see anything on it even if it was projecting full white. I've never done a direct comparison to felt.. just thought i'd throw out another option.