A 20 standard?
A pair of Cryptoheros nanoluteus? They're pretty sweet IMO.
A pair of Bolivian rams or blue/German/gold rams.
A pair or trio of Apistogramma species.
A pair of Laetacara dorsigera or L. curviceps.
For African options:
A pair of African butterflies (Anomalochromis thomasi)
A pair of kribs.
A pair of Neolamprologus caudopunctatus or N. leloupi (that's leloupi not leleupi).
A pair of Neolamprologus pulcher (Daffodil, syn. N. olivaceous) or Neo. brichardi or Neo. splendens (syn. N. helianthus) or Neo. gracilis or Neo. marunguensis.
A pair of Julidochromis transcriptus, J. dickfeldi, J. ornatus or J. marlieri Gombe (also erroneously known as J. transcriptus Gombe).
A pair of Lamprologus signatus.
A trio of Lamprologus ocellatus, Lamp. stappersi (syn. Lamp. meleagris), Lamp. speciosus, Telmatochomis vittatus, T. bifrenatus.
A small group (3-6) of Lamp. multifaciatus, Lamp. similis or Lamp. brevis.
Or for something out of the norm maybe a pair of Orange Chromides.