It is sort of possible, but because the projector is very close to the wall, every unevenness and bumpiness will be quite visible. E.g. a curve in the wall will distort the image, a bump on the wall may even have a shadow above it. Just try to point a flashlight on your wall from below.

(This problem is less visible with long throw projectors.)

Hello J.Francois,
that is possible but doesn't make sense. The picture will be bland and the room will have to be darkened despite the high light output of the projector. It will be slightly better with a normal screen. However, only a screen specially developed for these projectors makes sense. Have a look at Wemax.com, that's where I got one.