The code would be quite simple.
<plugin clsid="{95976968-45D5-40c9-9779-2B859B1C2FEC}" name="Full page image plugin" height="213">
<background bgimage="\Application Data\Home\image.jpg" />
</plugin>
Insert this code into one of your homescreens (at the very top, right after the colorscheme section). You should then be able to use Facade Settings' plugins list to insert it into other layouts automatically. The image used is in \Application Data\Home\, named image.jpg (you can also change that path of course).
Hope this works
