MDM is the default display manager for Linux Mint. It beautifies Ubuntu’s default boring Login Screen and make it easy to change themes.
To install MDM on Ubuntu 13.10, press Ctrl+Alt+T to open terminal, then follow the below steps:
1.) Add the stable ppa by running this command in terminal:
sudo add-apt-repository ppa:gwendal-lebihan-dev/cinnamon-stable
2.) Update the package lists:
sudo apt-get update
3.) Finally install the greeter:
sudo apt-get install mdm
You’ll be prompt to choose MDM as default display manager.
After that, you can download MDM themes from gnome-look.org and install them via MDM Preferences utility.
Enjoy!