What you have fits for sure. I think I read somewhere that black skirt tetras are from the same region. But those are a bit beefy so it limits the size of the school . Not that the rams would mind, mine don't get stressed by other fish like my male dwarf rainbows who are pretty big and fast. They just don't care. I have rummy nose tetras with them as well, and a few Yamato shrimps. The rummy nose look awesome and the rams ignore them completely.
But I like a big school of fish, so the more the merrier. In order to not overload, I would go with a bunch of tiny slender tetras. I just added gold tetras in my other tank and they are stunning.
I"m a big fan of Harlequin Rasboras, these guys always look great. You're mixing continents, but these guys are hard to beat.
I would stay away from the blue tetra (Boehlkea fredcochui) and other fish of such psychotic nature who behave like they are overdosing on cocaine and red bull all the time. At least the dwarf rainbows calm down after a while...
Eggs survive every time now in my tank: the flat rocks are surrounded by rocks, wood and plants and are place in each corners. Makes things easier for them.