I like the black neon tetras, Lemon tetras are beautiful, Cochies Tetras are blue and very different, but they maybe have to be ordered online. There is a jelly bean tetra that is really cool looking too.
If you go to the main page of fishlore on the right there is a list of fish and a lot tetras there that you could look into.
Just make sure to keep the peaceful ones together. Some tetras can be fin nippers and you don't want them in with ones with big fins. So research any that you put into your tank.
Thank you for all the suggestions I didn't know how big some tetras got except for neons & if any other ones would fit since 10 gallon really isn't that big, I'll do some research on the ones everybody suggested & see whats at my LFS then go from there.
I'm with aiylie, I would get black neons. Even with seeded filters off of the 29 gallon you currently have, cardinals are a bit more sensitive to water parameters than their black neon cousins and are usually recommended to well established tanks. And with the BNT's... you still get that pretty iridescent stripe =)