The GDM theme for RHEL5 is pretty cool. The one for Scientific Linux 5 is too "scientific". The one for CentOS5 is nice. The one for Fedora 7 is too "out there". Black Minimal is cool, but there's no feedback to if you're typing your username or password. There are some available that are either too flashy, too boring, or too Ubuntu. So, I found a nice template (Blue Swirl, which is based on Pixel Girl) to mod and created my own GDM theme called MookiePlain (creative, huh?). The only thing I really did was remove the background image and insert a black background. It makes the theme elegant, simple, and quite usable. You can get it here.