I was wondering about moss in enclosures too, as I found a few neat moss plants on Josh's Frogs website that would be a neat little finishing touch to an enclosure. They would do great in a chameleon cage because of all the misting going on. As for your question though, I'm not sure if it would thrive all the way at the bottom. Maybe someone could chime in on this?
If you DO want a plant at the bottom though, I've seen lots of people who planted Baby Tears because they grow like a wild fire and don't require a whole lot of light. You can probably find them in most garden centers or plant nurseries. Baby Tears has a moderate to high water requirement, and should not be allowed to dry out. Baby Tears can grow in a wide variety of lighting conditions, but more intense light will result in a more compact, lower growing habit and lighter green leaves. Baby Tears can function as a ground cover in the front of a tank, and does not need air circulation.
I'd like to know about the moss as well cuz I was gonna put one in my enclosure, about 1/4 way up from the bottom.... Just didn't know if it was even safe because I never saw it on the SAFE PLANT LIST for chameleons on all 3 sites I checked. Maybe someone else can give us both some insight into both of our questions...