I'd also like to see smaller critters like snakes or even smaller mice and insects that serve as prey for "mobs" they can all be weak and die with 1 hit and just exist to make the world look alive.

Birds that fly off if a mob or a person gets close.
Snakes/lizards crawling in the grass/on rocks.
Rabbits that things like wolves will attack and eat.
Hell! make some critters poisonous and will sting you if you run on them.

Small touches matter~