We've got Uther as a Starcraft medic, Vampire Countess Kerrigan (themed after one of the battlefields in the game apparently) and "Infested" Tychus.
What are some fun ideas for themed sets of alt-skins for the characters?
I think it might be cool to see Tassadar as a Diablo-universe Angel.
EDIT:
I wonder if we'll see a Jim Raynor Murloc Skin.