For instance the GdmGreeterTheme.desktop
Description=Theme with blue circles
Copyright=(c) 2002 James Smith
To test the theme you built, you need to install/yum the Xnest package. Once installed, type:
gdmthemetester xdmcp "theme-name"
If you like what you saw, to set it for good, edit the gdm file in /etc/x11/gdm/gdm.conf:
In the xml file, you can modify the row of buttons.
Position if changed from -0 to 0 moves from right to left
Anchor will put it on certain area on the screen. Possible choices are: N, S, E, W, NE, NW, SE, SW
To remove the log on loading box when you first login, edit the file located in /usr/share/pixmaps/splash/gnome-splash.png
To modify the screen resolution, the settings can be found in the /etc/x11/xorg.conf file.