From 1947, here's Pete Costanza's art on WHIZ COMICS# 91, a nice example of an infinity cover.
That is, the cover shows Captain Marvel reading the same comic we are looking at, with the result that the cover of the book he's holding shows a small view of him holding the same comic, which in turn shows a still smaller view, and so on into infinity (or until Morgo, Tyrant of the Microverse, objects at this intrusion). This particular example is appealing because of the simplicity of its execution and because the comic held by the Big Red Cheese is at an angle. This angle adds to the sense of infinity, as we seem to be diving down into the series of covers (look at Cap's hand, it almost seems to be moving).Infinity covers were popular through the Golden Age, before super-heroes became too serious and self-absorbed for their own damn good and lost most of their playful spirit. You'd sometimes see the effect on slick magazine covers and in cartoons.. Charles Addams did one showing a barber shop with mirrors on both walls so that you see a series of diminishing reflections in the chair. (And this being Addams, one and only one of the reflections revealing a smirking werewolf)
Collectors are funny (this is not the best-kept secret since D-Day). Just as some search for anything to do with Bettie Page or Buddy Holly and nothing else, some only want EC Comics with Wally Wood art and some will not sleep easy until they have every appearance of Hot Stuff the Little Devil (no, seriously). There are collectors who aren't that intererested in the comics in themselves as they are in building an assortment whose covers show skulls or gorillas or girls getting spanked. So I'm sure there is more than one fan out there with a beautiful collection of nothing but infinity covers.