The photo, which sees Cavill during his audition to play Superman in "Man of Steel", is later captured and shared by fans via Twitter.
"First test with Henry...I knew right away he was my Superman," Snyder wrote in the caption.
Cavill will reprise his role as Superman in upcoming "Justice League" and "Man of Steel 2".
"Justice League" will also feature Ben Affleck as Batman, Gal Gadot as Wonder Woman, Ray Fisher as Cyborg, Amy Adams as Lois Lane, Ezra Miller as The Flash, Jesse Eisenberg as Lex Luthor and Willem Dafoe as Nuidis Vulko.