One of the coolest wallpapers i have. Im using windows 7 now so unfortunately i cannot have two different wallpapers when using two monitor set up and it does not scale them properly...
Whenever I wanted to have different images on each screen, I made a single combined image, using a screenshot of my desktop as a template for where to place and how to scale each image. The result is big enough that you can tile it and it'll cover both/all screens while looking as a different image on each screen.
EDIT: Yeah, your post is a week old, but I thought the idea might be of help anyway.
mhm. that's a possiblity.
I was using windows 8 before my computer crashed and they under warranty they installed windows 7.
Win8 is much better in handling multiple screens (allows easily set up different walls on different screens).
Your method is workable but i have hundreds of walls so merging few of them would take a lot of work.
there is a program though which allows one to set up different walls on win7. haven't check it myself yet.