PVC pipes work nice, both as hides and water cup holders (just glue a short section of it to the bottom of a tank, and it prevents the snake from toppling water bowls and getting water everywhere). Also, if you cut a long piece in half length wise and put it in your cage with one side of it on the warm side and one side of it on the cool side, the snake can change position without ever showing itself, which will make it feel more secure. This is especially good for those real nervous types.
Super sculpey is really cool stuff, you can bake it and it turns into a light sandable material that holds paint very well, though I don't paint mine, since super sculpey comes in so many different colors. It's a little pricey though, a small box of the stuff that holds about a lb is something like 12 bucks, but maybe that's just the college art stores trying to rip us off.
I have an old combat boot that was never worn because it was too small in one of my snake cages and my snake loves to hide in that.
-13mur 6