Next up in DC Comics’ variant cover themes is, for some reason, not a subject or style, but an artist: Darwyn Cooke is doing landscape covers for a ton of DC’s December comics, including The Flash #37.
I first encountered Cooke’s retro 1950s-style art on the miniseries DC: The New Frontier, which I highly recommend. It links the appearance of super-heroes with the dawn of the Space Age, complete with the early Cold War and the societal upheaval going on at the time. Look for the collected edition or pick it up digitally.