just like in a garden you buy the plant to fit the site rather than change the site to fit the plant 
pothos (it's cousin, philodendron is toxic), spider, ferns and place the plants that need more light closer to the top or put a separate light for others down low. I know some people will mount a strip light sideways on the cage to light those lower down. Rule of thumb: variegated plants (mottled 2-3 colors on foliage - like pothos) can tolerate lower light. And the larger the leaf the lower the light
In my 4' I had schefflera, ficus and hibiscus. I had a second set and just rotated them when they got leggy. Hibiscus typically require bright light to flower, but they can keep going even without. My hibiscus was only about 1' of the floor of cage and kept blooming for months - Luna liked the flowers.
Just make sure you do not get any poisonus plants. There are several websites with this info.
http://www.ansci.cornell.edu/plants/
http://envhort.ucdavis.edu/ce/king/PoisPlant/Tox-SCI.htm
http://www.anapsid.org/resources/plants.html
http://webhome.idirect.com/~chameleon/owners/chapter2-sub5.html
hope this helps!
lele
-----
Chameleon Help & Resource Info
0.1 Veiled Chameleon - Luna. She's now hanging from her big jungle gym in the sky
1.0 Beardie - Darwin
0.2 felines - Kyndra and Lita
0.1 African Clawed Frog - Skipper
0.1 Mad. Hissers and she is on the loose!
0.1 Chilean Rose Hair Tarantula - Rosa Leigh
0.1 Goliath Bird-Eater Tarantula - Natasha
?.? Pinktoe Tarantula - no name yet