Nothing Crazy, probably mentioned at some point, and I'd think sorta simple comparatively ( forgive me if I'm wrong, I'm no game dev and know only basic programming)
However, ambient audio, like tweeting birds (the grasshoppers coming in 1.20 are cool) maybe a longer range call from animals, so, that animal you heard, does exists in your world but its a call or noise you can hear from farther away. (could be cool for hunting maybe?) Other bug noises, Frogs at night ( in the correct climates). Smaller simple audio stuff, as ambience imo can bring so much in making the world feel alive. Would be SUPER dope to see eventually.