Karmic: System wide wallpaper for regular joes

Yesterday I have installed a Linux Mint like theme on my Thinkpad baby, I like the looks of that distro a lot, and I have tested it -very briefly- in the past.

I wanted to set the wallpaper as a global one, to held on the directory:
'/usr/share/backgrounds/'
but after copying the file there it didn't showed up at all, even after logging out and back in, etc, etc. Didn't try rebooting, but, rebooting a box in order to get a wallpaper selection to show up seems like too much.

After Googling for a while, it seems like the whole thing it is a little more complicated than that.
Tried deleting the file '.gnome2/backgrounds.xml' to no avail, again, even after trying with a logout and a login...

In the end, I had to edit via sudo the file:
'/usr/share/gnome-background-properties/ubuntu-wallpapers.xml'
Adding the following entry near the end of the file:

  <wallpaper>
    <name>My Minty Desktop</name>
    <filename>/usr/share/backgrounds/Mint_Dew_by_Zwopper.jpg</filename>
    <options>zoom</options>
    <pcolor>#000000</pcolor>
    <scolor>#000000</scolor>
    <shade_type>solid</shade_type>
  </wallpaper>

No need to logout, not to mention, a reboot... The newly added wallpaper showed up instantly along with all the others.

How To make your GNOME desktop wallpapers available system-wide
Wallpaper system wide in /usr/share/wallpapers?

Un-compressed copy on Image Shack