My old meeting room at work used to have a projector throwing the image onto a plain white wall, worked well and was awesome for unreal tournament (about 4m across).
The issue with projectors is always how well they perform in lit conditions. If you like to watch in cinema mode with dimmed or no lights then even a fairly modestly priced projector will be a pretty good experience. If you want something to work in a lit room then your gonna be spending big bucks to up the lumens and to be honest it will never really be that great.
What size area will you be projecting onto?
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We just used regular white emulsion although we did discover that you could get special paint that was supposed to give a better image, but it was expensive and the regular paint was good enough so we never bothered to try it.