Hi!
I've looked thru the forums and done some googling but I don't see an
answer THAT WORKS for this question:
How to change the default GDM background/wallpaper to some other image?
I've tried all the things listed in the forums and none of them works,
including (but not limited to) copying the image I want into
/usr/share/backgrounds/images then running this command:
gconftool-2 --direct --config-source=xml:readwrite:/etc/gconf/gconf.xml.defaults --set --type string "/desktop/gnome/background/picture_filename" "/usr/share/backgrounds/images/Fistmaster.FullHD.0190.jpg"
having done that either log off or reboot and voila! no change at all! :(