it is not very easy to change the background of GDM theme in fedora. The gdmsetup command is missing in fedora 11. Because the gdm is going under through rewrite process. Only way to configure the gdm is simply downgrade to fedora 8 or change the display manager to KDM. here is another simple way
Change the GDM Theme Background
Simply go System | Preferences | Appearance | Background Tab .
or right click and change desktop back ground . in the back ground selector tab there is a button called make default. Select your favourite image and click this button. Your GDM background image changed .
Is that fine..
The other GTK widget styles and other features are not configurable at this time. But it is the most featured greeter in fedora 11.
FEATURES of GDM
Can use finger print reader
can change the language
can view the startup log (if any errors happened).
can view the battery status
can view time
in the other greeter KDM
there is no option to select a language to login.