Comment 99 for bug 395299

There was a small utility (see comment #42) that was released for Ubuntu 9.10. Unfortunately, if the tool is missing in Ubuntu 11.04, it can't be fixed because new features are not added to released versions.

Ubuntu 11.10 will be using lightdm by default instead of gdm. So while you're welcome to open a bug explaining what you'd like lightdm to do, there's not as much interest or developer time to work on a graphical tool for gdm.

GDM 3 was a complete rewrite by GNOME of what used to be in Ubuntu and does not support theming. I believe LightDM allows for theming but it's so new that themes haven't really been written (no distro ships LightDM by default yet).