So, I had an idea for what I think could be a pretty cool campaign setting, but I need some serious help pulling it together and thought this would be the best community to point me in the right direction.
The basic idea is a city overrun by undead, quarantined within the city walls. No one knows what's going on in there, or if there are any survivors, so the king has assembled a group of adventurers (by whatever motivational means fit the characters, be it monetary reward, royal pardon for past crimes, etc) to investigate what's going on inside the city. The party is escorted through a side gate to the city, and then the campaign begins as they explore the city, investigating the cause of the undead outbreak and encountering survivors.
I think the best way to construct the campaign would be to make one continuous map of the whole city and allow the players to discover it block by block as they went where they choose, gaining objectives as they run into survivors and enemies. The interesting part would be that they'd have to keep track of where they've been, find ways to sneak around groups of enemies too powerful or plentiful to fight, make decisions about when to retreat vs fight, and most importantly, they'd have to find safe places to rest between encounters/sleep. I think it would make for a pretty unique, frantic campaign which allows the players a pretty free hand in making their own decisions.
The largest difficulty, obviously, is building the city. My plan was to steal structural elements from existing maps (walls, doors, flooring, etc) and construct the whole city from scratch. This, obviously, is a pretty ambitious goal, but one I think would be worth enabling the high level of player autonomy within the campaign world. However, I'm having trouble finding enough map elements to lift for my map. Any suggestions on where to pull urban map elements from, specifically of roughly similar artistic styles?
I'd also be happy to hear suggestions about what sorts of buildings, encounters, survivors, etc to put into the city. I've got a fair number of ideas, but the more to choose from the better!
Thanks in advance everyone, for both the logistical and conceptual advice! This project is obviously in the very earliest stages of development, and any advice, suggestions, or other input at all would be incredibly welcome!