Linux Mint 13 has introduced a new display manager called MDM, that supports themes just like the old GDM 2.20 (which has been used as the base for MDM. If you want to use it in Ubuntu, here's how to install it.
Before proceeding with the installation, here are some screenshots of GDM themes used with MDM:
Install MDM in Ubuntu 12.04
MDM (Mint Display Manager) can be installed in Ubuntu using the official Linux Mint 13 repositories, but to avoid any conflicts that may occur by using the Linux Mint repositories in Ubuntu, I've uploaded MDM to a PPA so it can easily be installed in Ubuntu. Add the PPA and install MDM in Ubuntu 12.04 using the commands below:
sudo add-apt-repository ppa:nilarimogard/webupd8
sudo apt-get update
sudo apt-get install mdm mint-mdm-themes
During the installation, you'll be asked if you want to use MDM or LightDM (or other installed displayed managers) so select MDM. If later on you want to go back to LightDM or some other display manager, see: How To Switch Between GDM, LightDM Or KDM In Ubuntu.
After the installation is complete, restart your computer.
You can configure MDM by launching the "Login Window" configuration tool from the menu / Dash ("mdmsetup").
Install more MDM (Mint Display Manager) themes
You can download more MDM themes from Gnome Look. To use a theme, you'll have to extract the downloaded archives because you'll have to make some changes:
- rename the "GdmGreeterTheme.desktop" file to "MdmGreeterTheme.desktop"
- open "MdmGreeterTheme.desktop" with a text editor and change "[GdmGreeterTheme]" to "[MdmGreeterTheme]"
Once you're done, archive the theme folder to .tar.gz and use the MDM Configuration Tool (mdmsetup) to install the new theme:
Note: when renaming the .desktop file, it may automatically be renamed to "MdmGreeterTheme.desktop.desktop" - if that happens, use the terminal to rename it to "MdmGreeterTheme.desktop" (a single .desktop) using the "mv" command.
Thanks to fossfreedom for the tip; info via askubuntu