Another film that likely inspired some of the visuals of SW 1977 is Sergei Eisenstein's Alexander Nevsky from 1938.
In that film the main villains are the Teutonic Knights, the vanguard of a German army that is invading Russia. The plot of the film concerns Russian prince Alexander Nevsky's repulsion of the German advance. The movie's climactic battle occurs on a frozen lake, so it's rather reminiscent of the Battle of Hoth in ESB.
The Teutonic Knights are dressed in white robes, and carry shields and broadswords. They were likely the inspiration for the white-armored stormtroopers of the 1975 second draft, who also carry shields and laser-swords.
Also, in one scene, the white-clad knights and white-robed German priests lynch old men and women, and throw babies onto bonfires. This orgy of violence is orchestrated by a black-robed monk.
The contrast of white and black robes among the villains is reminiscent of the appearance of Darth Vader, surrounded by his legions of stormtroopers, in the opening of SW 1977.
Prince Alexander's strategy for defending the town of Novgorod against the Germans is as follows: "I know nothing of defense. We'll attack instead!" This is exactly General Skywalker's strategy for defending Aquilae in the 1974 rough draft.
The ruler of Novgorod is referred to as "Lord Novgorod," which is similar to how Leia Aquilae is the princess of the planet Aquilae in the rough draft.
The Russian men all have bowl haircuts, much like the hairstyle Luke Skywalker sports in SW 1977. The women all wear their hair in two long braids, like Kriemhild in Fritz Lang's Die Nibelungen (and presumably Leia Aquilae in the 1974 rough draft).
Finally, I don't know whether this was the case in the version Lucas saw, but when I watched the film, the subtitles were extremely archaic, with lots of subject-verb inversion. I wonder if this film's dialogue wasn't the inspiration for Yoda's speech pattern.