Dogs should bark, a lot, especially at night, specially when you are trying to sleep.
If you kick a dog you should get a stylish black cape, or spontaneously grow a goatee and curled moustache, or perhaps spikes should grow out of your armour…
There should be clowns, and mimes. Not zombie clowns or mimes, just ordinary ones, wandering around, and being ignored by everything. No lore, no unusual interactions, they are just there…
There should also be living statues, They are not ignored, if they move, they should just be desperately sweating in their boots hoping that they can move again someday.
There should be a living statue start. You start with nothing but a couple of low0coverage items of clothing, some body paint on the ground next to you, and a horde, possibly several, centred on you. You do not get attacked so long as your only action is to stand still. Once you take any other action then it is normal survivor mode with full zombie aggression. Maybe throw in some portals in your vicinity…
Maybe add a mutation on this, so that standing still while covered in body paint makes you completely invisible to anything that didn’t see you before. So basically it stops things from noticing you, but if they saw you before then they still know about you.