A planted community tank, tropical or sub tropical, would be awesome. For subtropical you could do your choice of corydoras for the bottom...you could probably have 20 corys in there, and they will be extremely happy!! For the middle you could do a large school of tetras, your choice here...And hatchetfish/butterfly fish for the top...of course many other options then I just mentioned.
Another idea is a planted tropical tank. 5-7 discus, some rams, angelfish, etc. And some delhizi/senegal or other smaller bichirs for the bottom, would definitly be neat.
Another setup is to go with a biotope, such as western african riversystems. Delhizi bichirs, african brown ghost knife, butterfly fish, congo tetras, synodontis catfish...your option list is definitly large! goodluck!
-Jesse