For my chameleon Larry, I use the big jungle vines you can buy at petstores. They're bendy, and made out of a spongy-foam like material, but look natural. I love them, easy to clean and he can grab them really well.
I also use a large fake plant with large stalks that he can climb up and down, and a big hanging pothos plant. Pothos plants are vine-y and grow like mad, great for chameleon cages. They retain humidity well too. I have at least one in all my non-snake cages
I'm with Brock on the tank though, it's just an excuse to get something really neat like frogs or geckos
My chameleon is in a large (taller than me anyway) cylindrical mesh screen and wood enclosure...
Good luck!
-Heather