Which range in particular? Ancients?
I used some Mirliton horses recently for Aventine cavalrymen... no problem.
Etruscans mix well (IMHO), but it depends, i.e. for my Carthaginians Aventine legionary imitation are tall, not a problem because they have a unit of their own.
It depends... and I like to mix/convert but I know it's not for everyone.
Ciao