First you'll need to know which type of tree frog you'd like to know their housing needs...temp and humidity.

Here is a nice starter article...
http://www.frogforum.net/content/choosing-frog-147/

A great plant for tree frogs is a pothos. They grow easily in vivariums and they provide nice leaves for them to climb on and sleep among. They must be rinsed of all fertilizers and pesticides.
http://www.google.com/search?q=potho...20&bih=444

Of course, there are many other options as well.

Black Jungle
http://blackjungleterrariumsupply.3d...homeSubCat_1_1

Joshsfrogs
http://www.joshsfrogs.com/live-terrarium-plants-1.html

New England Herpetoculture
http://www.neherpetoculture.com/plants