The others have made some great suggestions so far, and there's certainly a lot of ways you could go with this to make a very nice cage. I would share Cody's concern about the heat being able to penetrate the wood, but I'd think one way to deal with that would be to create a "false floor" of tile or shower surround about 1/2" above where the wood is and have the heat pad in between, or another way might be to use a drill to create numerous regularly-spaced holes in the floor to allow the heat through and then use ceramic tiles to create a heat-conducive floor.