My advice is go and do some research on human cultures outside of the standard European Medieval with maybe some Feudal Japan over there template, and incorporate them into the campaign as your main cultures, human or otherwise. All sorts of great stuff out there - pre-colonial India, the Byzantine Empire, Ancient Eygpt...or better yet, more obscure ones.

For a great city, look at Sarejevo or maybe 15th century Granada instead of Rome or London. There's endless possibilities, and historians have already done most of the owrk for you.