It's hard to get corals to start growing on the back wall without gluing them on, except for mushrooms or anemones. I've seen people glue zoos, and lots of SPS, especially Monti Caps on the back wall. They look terrible at first, but as they start to grow they look really neat.
If I remember correctly, you have a fairly small tank, right? You might not have a lot of room for SPS to be glued to the wall.