Hey Zemke. Do a search of previous OpS posts. I seem to remember this was addressed before.
I believe the solution was that you had to copy in the SS art folder from a PzC game (like Kursk) that had SS units in them as the original PzC Kharkov game does not have any SS units. Once you did this I believe you still had to tweak some of the names of the art to correspond with what Marquo used.
Or . . . somebody can send you the folder with all the work already done. I would do it if my computer did not crash a couple months ago and I lost it.