Some photos from Alexander Nevsky to illustrate its visual influence on the various iterations of SW:
Vasily Buslai, one of the supporting characters, sports the bowl haircut typical of Russian men in this film. Luke Skywalker ended up with a similar haircut.
Typical Russian women with their hair braided, much like Kriemhild in Fritz Lang's Die Nibelungen--a hairstyle also intended for Leia Aquilae in the 1974 rough draft.
The film's antagonists, the Teutonic Knights, wear white robes and carry shields, like the white-armored, shield-bearing stormtroopers of Lucas's second draft of SW.
The scenes of white-clad Germans murdering Russian peasants happen under the eyes of a sinister black-robed monk.
The Russian soldiers (Alexander Nevsky is center in the photo) wear helmets that leave their faces visible, allowing the audience to identify with them.
On the other hand, the Germans wear quite Nazi-ish helmets that conceal their faces, making them into a nightmarish Other. Lucas borrowed this idea for the Rebel and Imperial pilot costumes in SW 1977.