If you're planning on using a uniform dot configuration (something a wallpaper might do) for your dot room and you plan on also having actors in the room-- you'll be spending a lot of time putting uniform dots on your actors so they're able to better blend into the room.
Random dots work better in dot rooms because it allows the actors to better blend into the room because there is no uniform dot configuration to match. It's all random and the actor blends into the scene no matter where they're standing. My only suggestion if you're going to use the wallpaper is to add paint to the wall paper to make things a little more "random", so you won't have to spend so much time on the actors.
Ultimately, wallpaper or paint OR a combination of the two would work to varying degrees. The question is how elaborate you're going to get and is it worth your time. That balance of resources (time, materials) vs. scare factor/realistic scare is always up to the haunt owner.