24 Gallon SW Bio Cube Tankmates

Clowns are always fun. A pair of Percula or Ocellaris is always a good start.
A shrimp/goby combo. In all honesty, were it not for the fact that i already havre a clwon and the addition of another shrimp and a goby could damage bioload, i'd do it. I na larger tank the relationship is often lost (tanks so big you can't find the little guys!) but a smaller tank is great for it.
Firefish, of course. Small guiy with alot of personality. Also, the coloration when they're happy and relaxed is breathtaking.
Neon gobies. Very cute, active swimmers, fun to watch. Stay fairl small as well.
Jawfish. Might want to think a little hard on these guys, but again, tons of personality. need a deep sandbed though...However, they love to 'people watch', tons of personality, and fun little quirky habits.

Hope this helps.