Suggestions for animals in a river tank

[Double J]

Again, keeping day geckos or anoles with the toads would give you the "New World syndrome"... as these animals would likely die due to internal bacterial and parasite issues from living in an environment in which exposed to each others feces. IT is much like the way you get sick if you go to mexico and drink the water. Though the Mexicans can deal with teh bacterial load, we cannot as we are not used to it. Plus, anoles and day geckos prefer far warmer tanks than do the toads. These lizards mentioned need basking spots in the high 80's and low 90's. The ambent tempereature in the tank would simply be too much for these frogs. Firebelly toads prefer temps in the low 70's and will stress out if kept in the mid eighties for too long. Heat stressed frogs are not a pretty sight. Plus, the fire belly toads would tox these lizards out.
As for CamHannas suggestion... the anoles and green tree frogs..... again.... though they do come from the same geographical region, they inhabit far differnet *microclimates.* The treefrogs generally inhabit cooler shadier areas during they day out of the sun, while the anole are out basking directly in the sun, chasing around insects in the warmth. Creating both of these microclimates in such a small tank is next to impossible. The needs of one species would be compromised for another either way. It is far easier just to stick to one species. You will have far fewere headaches, and no dead animals.
If you would like to put some aquatic snails or small fish in the tank such as guppies, danios, or white cloud minnows, you could easily get away with that. Those would be the only other species would ever consider mixing with these por any other frogs.

Good luck... and keep the questions coming.