How to change the gnome login background?
 

Could anybirdy here please specify how to change the background figure when login the gnome session. That is the background behind the gnome login splash image. Thanks a lot!

If this is the "background" behind the login manager itself (gdm), then you could find out which theme you're using (by going to gdmsetup (as root) or by using the gdm configuration button which *might* be present on the login manager itself), then going to the theme's xml config file (usually under /usr/share/gdm/themes/themename/themename.xml) and editing it by hand, replacing the current background image by one that you'd prefer. Or copy the theme, edit it and then install it as a new theme!

If it's the image behind the Gnome splash as Gnome is starting up... then I'm afraid I have no idea as I've never tried.

You just need to configure your login screen. There is an option for that in the action menu of GDM. Goto the GTK+ tab and there is a box that will let you choose the background color.