Trisquel Awen wallpaper trick

I really like the way that Trisquel uses to setup the three different wallpapers, at least on the Awen release.
It uses a simple png image with the 3 color variants, to use it on Ubuntu it goes like this:

## sudo cp trisquel.png /usr/share/backgrounds/
## cd /usr/share/backgrounds/
## sudo ln -s trisquel.png trisquel-blue.png
## sudo ln -s trisquel.png trisquel-violet.png
## sudo ln -s trisquel.png trisquel-orange.png
## sudo ln -s trisquel.png trisquel-green.png

And then, on the file:

/usr/share/gnome-background-properties/ubuntu-wallpapers.xml

You need to add this:

  <wallpaper>
    <name>Trisquel Awen green</name>
    <filename>/usr/share/backgrounds/trisquel-green.png</filename>
    <options>zoom</options>
    <pcolor>#002F19</pcolor>
    <scolor>#8EC500</scolor>
    <shade_type>vertical-gradient</shade_type>
  </wallpaper>

  <wallpaper>
    <name>Trisquel Awen violet</name>
    <filename>/usr/share/backgrounds/trisquel-violet.png</filename>
    <options>zoom</options>
    <pcolor>#AA004E</pcolor>
    <scolor>#140016</scolor>
    <shade_type>vertical-gradient</shade_type>
  </wallpaper>

  <wallpaper>
    <name>Trisquel Awen orange</name>
    <filename>/usr/share/backgrounds/trisquel-orange.png</filename>
    <options>zoom</options>
    <pcolor>#E29E00</pcolor>
    <scolor>#B00C00</scolor>
    <shade_type>vertical-gradient</shade_type>
  </wallpaper>

  <wallpaper>
    <name>Trisquel Awen blue</name>
    <filename>/usr/share/backgrounds/trisquel-blue.png</filename>
    <options>zoom</options>
    <pcolor>#19387F</pcolor>
    <scolor>#5691C2</scolor>
    <shade_type>vertical-gradient</shade_type>
  </wallpaper>