We think the less travelled paths are more interesting. The "desolate wasteland with mutants/zombies" one has been done too much.

One setting that we've not seen much is one that isn't merely humans exterminating most of each other through nuclear war. Nuclear war on that scale would probably destroy all life as we know it. What we think would be much more interesting is one in which, either naturally or human-triggered, supervolcanoes erupt, creating a new cold era, maybe even an ice age. A single known supervolcano probably wouldn't be enough to do that globally, but if two-three such are triggered, there ought to be more than enough ash thrown into the atmosphere to cool the earth dramatically. 

It sure would solve global warming, at least.

To spice the new story up, we see no trouble involving things like magic in the aftermath of it.