I'm using this link but seems to be not working on 12.04, here's the Terminal message below: Are there other softwares/tips for changing the login screen? I'm also using link but seems outdated.

Failed to fetch http://ppa.launchpad.net/claudiocn/slm/ubuntu/dists/precise/main/source/Sources  404  Not Found

W: Failed to fetch http://ppa.launchpad.net/claudiocn/slm/ubuntu/dists/precise/main/binary-amd64/Packages  404  Not Found

W: Failed to fetch http://ppa.launchpad.net/claudiocn/slm/ubuntu/dists/precise/main/binary-i386/Packages  404  Not Found

E: Some index files failed to download. They have been ignored, or old ones used instead.
law@ubuntu:~$ sudo apt-get install simple-lightdm-manager
Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package simple-lightdm-manager