Hey, didn't they tell you when you got into this hobby that all you would want to do is keep getting bigger and bigger tanks!?!?!? You can have more corals, inverts, and assorted fish and kiss your cash goodbye!
Don't overlook the personality packed into gobbies. They are really fun although they are not the most striking fish in the ocean. My personal favorite is the Midas Blenny but they are somewhat difficult to find. The diamond gobbies are inexpensive, lots of fun, never shy, but sometimes they will re-arrange your tank.
Or if you have sand you could consider a jaw fish. They must have sand and some little rocks to collect and they can be aggresive with other fish, but they are fun. I'll bet you could have a couple of damsels and a jaw fish.
Don't overlook damsels for a smaller tank. The blue or green chromis are pretty in their little pods and they are not real aggressive. You can keep the agressive damsels if that is all you have in such a small tank.