Since version 11.10 (release October 2011), Ubuntu uses Lightdm as its main login screen. In the standard version this screen comes with a fairly nice Ubuntu background and an Ubuntu 11.10 logo in the bottom left corner. If you want to personalize the login screen to your liking, change the logo or both, this can be easily done
This involves changing 1 configuration file and copying 2 images to a folder, that’s all. There are however a few things that you need to take into account or you’ll end up with a black screen without a logo, or in worst case the inability to login to Ubuntu. And we don’t want that.