The New York Public Library has just put hundreds of thousands of its
still images online as the NYPL Digital Gallery:
"NYPL Digital Gallery provides [free] access to over 275,000 images
digitized from primary sources and printed rarities in the collections
of The New York Public Library, including illuminated manuscripts,
historical maps, vintage posters, rare prints and photographs,
illustrated books, printed ephemera, and more."
They're organized under the Library of Congress system, thus allowing
searches via its subject categories (including "Motion Pictures"). I
haven't found a lot of film resources, but there are dozens of
"cigarette cards" in both English and Afrikaans! And there are a few
photos of film theaters, too.
Plus, the Helen Armstead-Johnson theater photograph collection includes
stills from silent movies with African-American casts, such as SPITFIRE.
For past messages, visit the Screen-L Archives: