I'm using Wallch to cycle through all my photo's and it works really well. However when i shutdown and come to login next, the login screen shows the last photo that was being shown.

I don't want this to happen and the only post i could find has a dirty solution, i don't want to change the permissions for 1000's of photo's.

I have also tried using scripts that run at logout and although this works, the scripts run after logout. I set the desktop back to original using the following commands.

gsettings set org.gnome.desktop.background picture-uri 'file:///usr/share/backgrounds/warty-final-ubuntu.png'
gsettings set org.gnome.desktop.background picture-options zoom
Next time i login my desktop is set back to the warty ubuntu wallpaper, however the login screen still shows the last picture that was on my wallpaper, so it must being set somewhere before logging out and it mustn't be being read from the gnome desktop settings. Does anyone know how to disable this or where the setting is likely to be stored so it edit it with my logout script?