I can see where you're coming from, I've put some stuff in some of my snakes' cages for them to play with.
My boa has a whole bunch of those sanded grapevines they sell for reptiles. In my corns' cages, I put a paper towel tube and several squares of styrofoam insulation. It gives them something to occupy them to discourage them from trying to get out the top.
However, on the top of those 3 cages are bricks. Some people would think this is overkill, but the 2 corns and the boas are the most apt of all of them to try to escape.