There is a bug in the current release of the GDM (Linux) Screensaver and it shows ONLY the default background. Not the current one like it is supposed to.

The hack for this is to copy what you want to the following file:
/usr/share/pixmaps/backgrounds/gnome/background-default.jpg
at least that is what the page below says.
Arch Linux Forums / Lock screen?

That did not work on my Ubutntu based retool, EasyPeasy.
For Easy Peasy the following worked
root@host:/usr/share/gdm/themes/SleekDragon# cp /usr/share/backgrounds/easy-peasy-4.png /usr/share/backgrounds/easy-peasy-4-save.png

root@host:/usr/share/gdm/themes/SleekDragon# cp Sleek_and_Sporty.png /usr/share/backgrounds/easy-peasy-4.png

I’m currently using Sleek Dragon for my login page, so this worked for the screen saver as well. (great Job Michael Russell, aka Potemkin!!!) http://www.gnome-look.org/content/show.php/Sleek+Dragon?content=25716

The whole reason that I wanted this change is that the Easy Peasy logo is horrible. I like most of their work, but the graphics just don’t work for me.