:
Jan III Sobieski (who has been pseudo-confirmed):
Charles V (who could have a numerous amount of backgrounds considering how large his multi-lingual empire was):
Napoleon (I can't decided whether the classic hand in coat is better than the one of him on a horse. Now that I think about it, the latter was used for March of the Eagles):
Frederick II the Great (sadly without his tricorn):
Peter the Great (aka; history's most eccentric tsar. I wouldn't be surprised if the background was a shipyard in the Low Countries):
William van Orange:
Or they could just go with Maurice of Nassau, who was the basis of Res Publica:
George Washington:
Gregory XIII:
Abbas I the Great:
Babur:
Krishnadevaraya:
Kangxi:
Oda Nobunaga (if I recall, this was also the basis for his Civ V appearance):
Or they could always go Koei:
And Pachacuti, who'll probably be in El Dorado (another Civ 5 basis):