Hello Gunniz,
After you have downloaded and extracted (drag and drop) the
img0.jpg file from the downloaded ZIP from above to your desktop, you can copy it into the folder below to restore it back to it's default location.
C:\Windows\Web\Wallpaper\Windows
Afterwards, you can use the tutorial below to change the desktop background to this
img0.jpg file by clicking on Browse (step 3), navigate to the location above, and select the
img0.jpg file.
http://www.sevenforums.com/tutorials/281-desktop-background-change.html
Hope this helps,
Shawn