i just searched the forum and i couldn't find any topic related to dual monitor wallpaper, i'm sure there are many ppl out there using 2 monitors or even more so why don't you share your best dual monitor wallpaper ?
I have a triple monitor setup and I made my own wallpapers.
This is from the highest resolution photo of the earth by NASA combined with Nexus 7 wallpaper (left) and something I took a shot of (bokeh on the right). I am also a photography enthusiast.
my shots here: Flickr: Ganie B.'s Photostream