Screens have to be smooth. Pebble finishes are absolutely the worst. As the owner of an Optoma all-in-one projector (projector, DVD player, and speakers), I've taken the projector everywhere and projected on all kinds of surfaces. Green walls, blue walls, sheets, garage doors, shower curtains, anything flat. The worst surface I ever projected on was a light beige stucco wall in a hotel room. You wouldn't think it would be as bad as it was, but the pebbled surface scattered light all over the place. The kids still loved it, but I wasn't too happy. No question about it, you have to have a flat surface.
Jim
Now as a PS, I also have an Optoma Greywolf screen with a beaded surface. But the purpose of the beads is to reflect the picture back to the source (It's retroreflective). When we use this screen, the projector is on the floor along with most of the watchers. The picture is good, but if I stand, thus bringing myself above the screen, the picture loses an enormous amount of the WOW factor.