Well, is this going to be a reef or fish only? There are many larger fish that don't swim like tangs. If it's just a fish only, a dwarf lion might be a good fish for you. If you are going to keep shrimp and smaller fish, that won't work however.
There are many awesome looking wrasses that would work also.
Here's a good place to get an idea what you can keep. They have minimum tank req's and if they are reef safe or not-
Saltwater Fish: Marine Aquarium Fish for Saltwater Aquariums
As for tangs, the round bodied ones are better for smaller tanks, like purple, yellow, scopus, kole...