A look at what made Jack Kirby famous.
I don't think this is Kirby. I think this is Joe Simon swiping Kirby. See the cover to Captain America #7. It's not like Kirby to swipe from himself. I'm betting if I looked long enough, I could find the source of the leprechaun face as well.
Mark, I agree, and that tiny figure of the Fly above the logo is a swipe of the cover of Fighting American #2. As for the leprechaun, I know there was a story in Black Magic about a scary leprechaun, but I don't have it at hand to check.