Well you could use the very basic guideline - and I emphasize very basic (Because most people disagree with it) of 1 Inch per Gallon. In other words, for every one inch of adult fish you need one gallon of water.
So your average Platy gets to be around 2 Inches, which means that you have about 6 inches worth of fish you can get. Out of that list and from other lists for 10 Gal tanks I've seen I would say some of your tank options could be: (Note all options include 2 Platys)
Option 1
2 Platys
4 Pygmy Corys
4 Ember Tetras
---|>The thing with this option is that the other two types of fish I mentioned are both schooling fish and do better when kept in groups of 5 or more. Also, I've only rarely seen Ember tetras, so they're hard to come by (In my area anyways).
Option 2:
2 Platys
5 (Or so) Guppies (Preferably all one gender - Males are better, they're brighter and they cant be brought home pregnant)
10 (Or so) Cherry Shrimp.
This one looks better to me, as it ill be more colorful, the fish won't be sad because they don't care so much about schooling and the Shrimp are great bottom feeders and they are much lighter on the Bio-load.
Option 3:
2 Platys
5 Neon Tetras
10 (ish) Cherry Shrimp
---> The thing with Neons is that though they are small, they are active, and really (In my opinion) They need to be in larger groups in larger tanks. Though it is possible to keep them in smaller groups in smaller tanks, they just (To me) look nicer in a group of 20 in a 50 Gal tank.
Note: Any smaller Tetra, like an Ember Tetra can be substituted in.
Those are just some options, some may disagree with my numbers.