What fish would go well with platies and guppies?

I have a 20 gallon aquarium with two female platies, one male platy, three male guppies, one female guppy, and a baby platy. I wanted to get a new type of fish but do not know what would be okay to put with them. I have heard neon tetras can go with them I was wondering if there were any others. Also I was kind of hoping to avoid getting more live-bearers.