Two or three fish would probably be fine as long as they're small. There are lots of options, here are some I can think of: a clown goby, a pistol shrimp & shrimp goby combo, ocellaris/percula clown(s), many damsels, a bicolor blenny, neon goby...
Don't forget about inverts as well - they add lots less bioload and some have just as much visual impact. Cleaner shrimp, blood shrimp, sexy shrimp, emerald crabs, hermits... they'd all probably do well in a tank that size.