Some little touches I love in A18 that set the mood.
Flies at certain Dumpsters, small thing but highlight the decay in the world. (need more flies)
Zombies emerging from the water (sounds fx as well) kind of a scene from a zombie film I forget the name....
This game needs more gore set about the world, like hanged zombies or heads on pikes etc....
Also as there lots of easy ways to get fresh meat, you should make it that we have to store it in coolers, (thats behind a perk or book) else it becomes rotten meat....