We have winner, and his name is 2dMatty. Congrats! With 11 votes, you were on top of the list, closely followed by Misj' with 9.
Thanks for all the entries.
Armageddon: Your background has a gritty, expressionist tone which I like. The pencil strokes add to that. However, the irritating perspective and the details on the village are hard to read, so the functionality is, in some way, disabled.
Misj': You've done a beautiful 8-bit rendition there. The limited colours give your background value and contrast which I thought the original lacked. I can clearly see this image in-game. The 4-colour-version are a nice addon, but the dithering, I think, should have been the same resolution; now, they're double the resolution as the non-dithering pixels, which gives it an awkward look.
2dMatty: Great colours (although the bottom half is a bit too green for my taste), and the rain effect really adds to the scenery. Like Misj's bg, yours succeeds in telling a story.
oraxon: A chilling image. Everything is just hinted at with a few strokes, but yet it seems so well detailed that one can feel a cold, but soft wind on your skin.
Cuiki: I dig the alien looking building and the hills, but for some reason I'm not a friend of the foreground. There's nothing really interesting there.
Lad: That style works for me, and I could easily imagine it in an adventure. However, I'd like to see it with more details.
Eazy-O: My favorite of all. The Paint-style airbrush and the harsh colour scheme nails the post-apoc theme you were going for.