My tank is full of cories! I have loads of different species because they are all rescue cories. I have 4-5 bronze, 3 pepper, 3 albino bronze, 2 pandas and 2 sodalis (or something like that!) and 2 sterbai.
None of the species mix except when they are feeding at the front of the tank, other than that the species stay seperate!
Personally I like having groups of 4-5 of each species and 2 - 3 species but thats just me and depends how big the tank is.