I can think of the following additional video resources you could use if you're going to document any of the influences on the development of Star Wars:

-Hidden Fortress (there's even an interview with Lucas discussing this film on one of the DVDs of this)
-Triumph of the Will - the medal ceremony is heavily based on two scenes from that film.
-Fritz Langs Metropolis - for the origin of c3po - as portrayed in Ralph McQuarries early artwork where c3po is a direct copy of the robot from that film. Might be nice to show the evolution of c3po from metropolis robot, through mcquarries artwork to c3po proper.
-Original Buck Rogers serial for the origin of the title crawl
-Similaly the Flash Gordon serials
-There's also a possible vader influence in the villain from serial Fighting Devil Dogs

-Anthony Daniels segment of BBC4's 'Machine Men' might also be useful - thats one's still available on alt.binaries.starwars.

If you don't already know about it, I'd recommend this sites for more influences and info: Star Wars Origins

There's also this bit of trivia regarding Saint Tarkin

EDIT: I know you said no more titles but I'm going to throw out these two anyway:
A Long Time Ago....
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