I presume you want to keep a community tank? If so, what you'll probably want some top, mid and bottom dwellers, however, you won't be able to have too many.
Maybe you could have around three (SMALL) corydoras as bottom dwellers, a school of six neons as mid and possibly a dwarf gourami?
You'll need to ask about these in there specific forums, as I'm afraid I don't know much about these fish, or their maximum sizes.
Gouramis - Gouramis and other Anabantoids
Corydoras - Catfish
Neons - Cyprinids, Characins and Atherinids