Someone has already snatched the spr1s.
http://www.dom2minions.com/~minion/icons/
Note that there isn't a command to directly change the name of a national hero, which is sad. That's why most set-ups simply have the same name for national heroes and different art. I think that you can create a custom nametype and then define the new nametype as having only a single name in it, and then assigning that nametype to one national hero. AFAIK, that will only work for two heroes, however.
-Frank