new fish to add

i have a 20g freshwater tank that has alot of plastic plants (various green) a few big rocks, bluish green gravel. i have stocked with 5 neons, a red/orange swordtail and 2 yellow guppies. i want to add another school of tetras or any type of school and can't decide on which to get. i was thinking of pristella tetras because their whitish colour will contrast nicely with what i have

any suggestions!??