I think it would be cool if we could have vultures in the game that would eat all the dead corpses and fellow the player around if he is near death
Maybe
V
also Zombie Vulture
Birds cat become zombies/are too small to become zombies.
But having vultures around would be nice, especially if they are attracted to corpses. Could really add some good apocalypse flavor to step into a fema camp and spook all the vultures away as some sort of ill omen.
I like that idea a lot, actually. Carrion birds attracted to carrion would be neat. 
Crows are also nice.
We have crows in-game already. Vultures would be an acceptable extra if we had good “spawn around corpses” spawning behavior.
re FEMA camp, uh, John, I think the zombies would scare the vultures away anyway. :-/ Otherwise, yeah, good atmospheric idea.
On animals and such, it would be nice to have animals that eat stray food. Could be useful for animal-NPC relations, like a little dog.
I don’t think there are any creatures that actually interact with the surroundings other than “blow up” or “spread stuff around”.