It would be fun with themed city layouts. As in cities generated in different themes.
Initially a city size should be decided:
Village: Usually a very little gathering of houses around two crossing roads, very little branching off and the brancing off should mainly be based around roads leading to farms and such.
Town: A larger town situated around a landmark of sorts like a river or a mountain of sorts. Has a large suburb and a town center with shops and malls around, bonus points if the town center has a randomly generated statue of some important figure.
City: Very large with large suburbs and industrial areas surrounding a clusterfuck of appartment buildings, business buildings and stores.
Then we must define a theme:
Normal: as we already have it with very little damage, lots of zombies, etc.
Nuked: Very little activity, all houses heavily damaged or completely ruined, lingering fires and alot of radioactivity, in turn there should be alot of vehicle wrecks and corpses to loot.
monster type infested: Full of either zombies, triffids, fungals, swamp creatures. Signs of struggle and building damage very prevalent.
Ghost: Everyone disappeared for some unexplained reason! Maybe there could be some hidden artifact somewhehre, or horrors just waiting to eat you, be aware of theese deserted cities.
Out in the ass nowhere: A little village in the middle of nowhere, the inhabitants barely noticed! There should be alot more NPC’s. While this is a recipe for segfaults now, it would be much fun later.
War Zone: People are still fighting in theese cities, high npc and zombie count, military prescense, etc.
Wild: This city was evacuated effectively! There are almost no zombies, but instead has the mutated flora and fauna taken hold of it! Buildings overgrown and torn apart by vines and trees, lots of wildlife. Think the areas around Chernobyl.