Houses and shops:
Broken windows and rags in the smashed glass to suggest looting and people escaping their houses in the first days. Or zombies smashing their ways out after turning.
Boarded up windows and smashed windows or doors with zombies trapped inside. Some houses could have been fortified, but the zombies got in.
Drawn curtains, open windows, where people hid or tried to escape.
Half eaten meals on tables.
Burned food in ovens
Burned downs ruins from ovens left on or a cigarette being dropped.
Fortified buildings. Buildings with locked doors an stockpile of stuff and a dead human. Fortified building either have no food or no meds. To show how this human died.
General scenery:
Blood trails: Paths of blood leading to human corpses from windows or just stopping at some point.
More corpses: Surely not everyone turned. I mean come on. Maybe its just corpses with ripped gear on them. Torn backpacks. Damaged weapons. Ripped clothes and nothing really good.
More berries clustered together: Since when do fruit bushes only produce one fruit… ever. I mean they could re grow as well.
Mushroom clusters: One mushroom. Growing alone in a forest. Since when does that ever happen?
Poisonous mushrooms: So what you’re telling me is I could walk out into the forest. Pick up the first mushroom or toadstool I saw. Eat it and be fine? Okay.
Long/ growing grass. Who trims the lawns in the apocalypse?
Car crashes: Most of the cars in towns seem to have stopped just in time not to crash. Why not have metal wrecks surrounded by smashed glass and bits of metal maybe some damaged wheels. Ooh and pools of gasoline on the ground.
Cars through walls: I mean I’d probably crash into a wall if I was driving and I saw a zombie. Or I’d leap out of my car and it would crash into a wall.
Already dead Z’s: Nobody managed to kill any of these guys? Jeez whats with all the military stuff if they just stood there and watched?
Other Building generation:
Firestation: I want a fire truck. With and activatable siren.
Police cars: Sirens FTW
Extra Biomes:
Fungaloid Forest: An entire forest taken over by the fungus
Fungal Towns: Buildings turned to fungal beds with a giant 3 by 3 fungal spire in the middle.
Natural Battle grounds: Fungaloid/Triffid/Giant bug bodies. At least 2 species. Triffids and Fungaloids dont get on.
Fungal Triffid groves: Mushroom wins this round, trees.
Triffid Forests: Groves the size of forests
Triffid Towns: Overgrown buildings, grass everywhere. Evil Tree beasts and a giant 3 by 3 heart at the very centre of it all.
Creature Generation:
Zombie Animals. If it affects dogs it affects squirrels. Hoards upon hoards of Zombie squirrels. And all the other animals too. Zombie animals are static. The normal animals just keep spawning.
Weather:
Snow: Stuff that settles and changes the landscape. Some doors cant be opened in snow. Craftable snowballs. Can you imagine pelting snowballs at a zombie? Ive never survived until winter so Idk if thats in there.
That is all