I would advise you against the bristlenose, like someone said before they grow out of a 10 gallon. But, I've had mine for about 6 months now and he is still within the 10 gallon size range, so if you're planning on upgrading that should be fine.
I would recommend otos, they stay quite small and although I've never kept them, I hear they are fun to watch. There are also some really cool varieties out there (my favorite is the zebra oto) that you might be able to get your hands on if you look hard enough.
To be honest, I would take back your zebra danios as well. Even though they are small, they need a lot of swimming room (at least a 20 gal
) and if not, they could become aggressive. I made the mistake of having 5 in my 10 gallon once too, and the biggest guy slowly drove the rest to death from badgering. They just would thrive in more space.
Is there anything in particular you're looking for? A centerpiece fish, a school, or bottom dwellers?