Some possible styles to go for:
A rather picturesque map from about 1520. Perhaps something a monk would draw?
A map from ca. 1570 from the Ortelius maps. Rather simple, but quite stylish.
Mid-17th century, Joan Blaeu. Similar style, just more developed.
Or go for something a little more modern... 19th century styles are very well suited to depict political / cultural maps.