Knowing me, I can only suggest a colubrid. Here's a few I think would be great for an arboreal display cage. Gonyosomas, vine snakes, P. obsoletus, E. prasinas, rhino rats, rough greens (!), flying snakes...that's all I can think of for now. I'm sure there are some more.
The Herp Room
"The day I tried to live, I wallowed in the blood and mud with all the other pigs" - C. Cornell