"Kitchen sink" role-playing settings like
Rifts and
Synnibar are well known for their anything goes approach. While comic books have never got as freewheeling as those settings (well, their respect universes taken as whole are, probably), they managed to create some high concept post-apocalypse settings based on some really interesting mashups. What they lack an "anything goes" they make up for in greater coherence.
The world of
Killraven first appeared in
Amazing Adventures vol. 2 #18 (May 1973). It posited an apocalyptic future of mutants and sword-wielding heroes in thigh-high boots that resulted from a second Martian invasion after
War of the Worlds.
1975s
Hercules Unbound #1 reaches even further back for his literary antecedents to Greek mythology. Shortly after world devastating nuclear war, the demigod Hercules breaks free from where Ares had imprisoned him and resumes his fight against the evil god of war. Mutant humanoid animals are among the challenges he faces, and these explicitly establish the world of
Hercules Unbound as the same animal-dominated future as Jack Kirby's
Kamandi. Later, it was also linked to the world of the
Atomic Knights--which turned out to be a dream, so we'll ignore that.
Planet of Vampires (also in 1975) borrowed from
Planet of the Apes in having astronauts return to a future earth gone mad, but instead of being overrun by animals like in
Kamandi, it was dominated vampires like in
Omega Man. Of course, forgo the astronauts and goth it up a bit, and you've got
Vampire Hunter D.
Check out any (or all) of these for some fresh post-apocalyptic gaming inspiration.