What do you like?
Tetras?
Dwarf Cichlids?
Gouramis?
Livebearers?
Personally (wish I could set my tank up from new again) I would go a small schools of glowlight tetra (8), a small shool of rummynose Tetra (8), a pair of brislenose catfish, a pair of apistogramma (cacatoides) and a pair of German blue Rams. Plant the tank quite dense, get some CO2 in there, also lots of caves and/or bogwood for refuge and it will look ace! But thats just my opinion, guess its up to you what you like really flakes.
Cheers,
Bricko