Perhaps some rasboras would tickle your fancy? or some rainbow fish? A massive school of various kinds of rainbows would be quite the show (especially when they are mature).
What are your water parameters?
If your water is soft with low pH, Amazonians like cardinals or others from those waters would be great.
If your water is hard with elevated pH, Astyanax tetras from the hard waters of Mexico, or Buenos Aires tetras from south of Amazonia would be better.
Not the smallest but a large school of Colombian red’n blue tetras Hyphesobrycon columbianus) would be awesome in a large planted tank. Alternatively, rummynose tetras are awesome a smaller.