you have a lot of south american catfish to choose from. mostly corydoras species, but also things like spotted/striped raphael cats and porthole cats could be cool.
a school of 5+ cories is a must for a tank like yours
lots of tetras and rasboras. maybe even a pair of discus...
I think my main tank is somewhat SA with an angelfish, neon tetras, a cardinal, pygmy cories, bristlenose plecos, and the only thing that contradicts all of them is one female platy...ಠ_ಠ