I think zombes should fight sea monsters!
Okay, fine... still think there should be a sea monsters collection though...
What if, rather than going for a broader canvas, you tried narrowing the focus more?
For example... Permuted has done historical zombies, but what about a book of nothing but World War Two zombie stories, either subtle or strong?
--The horrible events around Pearl Harbor, when the Japanese fleets released thousands of undead on the Hawaiian base, forcing the Americans to destroy their own airstrips and buildings.
-- Hitler's attempt to take the Soviet Union fails when his zombie hordes freeze during the harsh winters.
--Rommel in the desert as ancient evil rises from the sands of northern Africa.
True Zombie Tales of the American Civil War?
Otherworld Zombies-- awful tales of the undead in space.
Zombies of the Carribean? What was the awful truth behind Blackbeard's legendary appetite? How did the phrase "dead man's chest" enter the pirate vernacular? What made zombies a tenet of certain island religions...?
That's all off the top of my head...