Ello again
I suspect what your loop needs is some filtering. Make the beginning a growing noise and then decrease it again slightly in the middle and once again at the end. That way the loop wont make the clicking noise (and might make it a bit creepier?).
Fading noise is pretty important if you want to maintain variation in your loop (even if it is a loop, it shouldn't sound identical all the way through), and I think thats what would set the song on fire.
You should make a full song with a zombie theme! :O
.... Maybeh? o,,,,,,,,,,o