The great fantasy blockbuster movie of 1924 The Thief of Baghdad (Fairbanks/United Artists, on general release from 23rd March 1924). Lovecraft must surely have seen this big-budget picture when he first moved to New York.
The film is now public-domain, and is available free on Archive.org.



Above: an undersea monstrosity encountered by the hero.
And the film’s depiction of the takeover of Baghdad by the Mongols finds a visual echo in the story “He” (written 11th August 1925)…
“swarming loathsomely on aerial galleries I saw the yellow, squint-eyed people of that city”

[ Hat-tip: John Coulthart ]