Nope. A lot of the fish you want would be best with a species tank...well not a lot, just the puffer and the seahorses. I don't know much about puffers or seahorses, but I'm pretty sure puffers could be kept with other fish in a large tank. It's just that your tank is small, so your options are limited. If I were you, I'd get a clown, and a neon goby or two. Or have the tank be a species tank for a baby puffer...when he gets too big, sell him to a local reefer or the LFS.
Just my .02