i do something similar all the time- having one for breakfast, as i type this!
here is my basic:
coffee ice cubes- half a tray makes a nice glass of frappe
cream, coconut milk or almond milk (whatever is on hand)
a splash of chilled coffee
sf torani- hazelnut or raspberry are my favorites for this
an extract- vanilla, raspberry, peppermint, banana, etc....
optional add ins:
cocoa powder with a dash of salt
if i went with sf caramel torani, i add in salt for a "Salted caramel frappe"
peppermint extract is great with cocoa- for a peppermint mocha frappe
cinnamon, with or without cocoa
i love to make "whipped cream" by chilling a can of coconut milk overnight, scooping off the separated cream and stirring in a bit of splenda