Polaroid of Mark Hamill cracking his knuckles, from the original Star Wars film, ~1976 (ten total, with fascinating 'making of' article)

I seem to recall Lucasfilm releasing hordes of behind-the-scenes photos in the 2000's, but somehow it was fun being taken back via the clumsy magic of these simple polaroids. Not to mention, Danny Dutch has been doing an outstanding job lately with these history articles:

https://www.utterlyinteresting.com/post/polaroids-from-the-filming-of-star-wars-episode-iv-a-new-hope