To get rid of the peasant when adding a unit from faction C to point D. You can go to data/ui/units folder and the unit_info folder.

Lets say you want to add the Cossack Musketeers from Russia and give them to England. Simply copying the musketeer files from Russia over to England, and ta-da! No more peasant pic. :)

Still trying to see if getting the units to APPEAR in a battle map will work the same way.