You could do a small number of fish or a small school of tetras such as neons or cardinals for example. Just make sure the fish are small enough for a ten gallon and it would be really nice if it was planted..
Peacock gudgeons actually grow to four inches, officially, though I believe barbie has ones that are bigger. There are other small gobies and gudgeons that would work.
Yah, I can quote you 3 other sources that say 2.5-3" max and rarely 2" in the aquarium. Barbie is probably giving hers roids! That's also based on the largest specimen found in the field not the average.
I know that plenty of other places say that. But fishbase tends to be the most reliable website when doing research on fish as it is held up to scientific standards. My guess is that they are stunted to that size by their living conditions. They are also slow growers-I think barbie had hers for 7 years or so. I owned one a while back.