Hello there.
I am the one who is creating the In-game backgrounds, wallpapers and misc textures. If you would like to download the file which adds the in-game backgrounds just go here (these were made after beta 2 was released):
http://www.megaupload.com/?d=JPPJ7I5A
Readme included.
These in-game backgrounds are meant for beta 2, so expect updated backgrounds once future versions of the mod are complete.
One of the wallpapers included in this addon: