Theres more to fish than the bread and butter species. Don't forget all of the little gems.
Cichlids:
A pair of the docile species of Apistogramma, Nannacara anomala, Neolamprologus brevis or multifastiatus (shell dwellers), certain pelvicachromis could work too. I'd be tempted to try a Laetacara pair as well, either curviceps or dorsigera.
Then theres shrimp, snails, gobies, native darters, ummm lots of option.