HOW TO EDIT A WALLPAPER FOLDER AND DEFAULT FOLDER

ADD THIS FILDE CODE:

<wallpaper>
     <name><NAME OF YOUR WALLPAPER></name>
     <filename>/usr/share/backgrounds/<NAME OF YOUR WALLPAPER>.jpg</filename>
     <options>zoom</options>
     <pcolor>#000000</pcolor>
     <scolor>#000000</scolor>
     <shade_type>solid</shade_type>
 </wallpaper>

INSIDE OF THIS FILE :

root@mac-os:/usr/share/gnome-background-properties# vi zesty-wallpapers.xml


MOVE YOUR WALLPAPER FOR THIS FOLDER
root@mac-os:/usr/share/backgrounds

and just try to change your wallpaper.