Discus get HUGE! They get to the size of a dinner plate. The man who sold me my 90 gallon had a tank of some discus and they were huge and beautiful. Brilliant fish if you ever have the space and time (and money lol $50 a fish).
You could have a dwarf gourami of some sort. They're very nice centerpiece fish. Honey Gouramis come in a nice yellow/orange and there's another that's electric blue, and have one school of small tetras or barbs. I've seen some people keep just a school of small cories. Of course, there's the fan favorite betta, but its really a 50/50 shot on if they like having tankmates or if it stresses them out.
If you'd like some sort of "clean-up" crew that isn't cories, I recommend Amano or Cherry Shrimp or Nerite snails. With nerite snails, you have no risk of any accidental snail babies and are pretty chill snails. I have one in almost all of my tanks.
For lots of bright movement you could always go for an all-male guppy tank. I wouldn't recommend females because you'll have babies coming out the wazoo!