Well considering that you've only kept small fish, I would recommend going with some semi aggressive cichlids and the like.
Cichlids like severums, geophagus, chocolate cichlids, uaru cichlids would love the tank space, and even an Oscar if an Oscar is your cup of tea.
Here is what I would stock in the tank if it was mine:
~ Severum Cichlids (1 to 3)
~ Uaru Cichlid (3)
~ Chocolate Cichlid (1)
~ Geophagus (red head tapajos, winemilleri, and any specie you like, you can do up to 6 or as many as you like)
~ Redhook silverdollars/Thin bar black bars/wide bar black bars or a big school of metynnis silverdollars
~ Bala sharks
~ Flagtail prochilodus
~ Pictus catfish
~ Lima shovelnose
~ Fancy plecos
With some driftwood, black sand as substrate, and some plastic plants, this would be a awesome sight to see fish tank.