Leporinus would make a nice addition to tank due to its different shape body. They tend to have them at the chain stores now and then, and they grow super fast. If you go in the way of a severum, try to get a super red to throw some nice color into that tank. Also, can't go wrong with a school of clown loaches
I've had several Leporinus species over the years, the only one commonly available is the banded, which is a very nice fish and gets big, is not too mean and will add a lot of color, I think that is one that's on my list for the tank. I have several loaches, but no clowns and probably will keep the tank S. A. only, but they are cool fish. Thought about pink-tailed Chalceus also, I nothing that stays at the surface.