But remember, GDM Tweaker does not work with the GDM version 3 but for all the Ubuntu 11.04 fans (including the below versions)... fear not my friends, this totally rocks!.
Main features... (well there aren't much... only 3 or 4 or may be 5 :P)
*. Change your background to whatever you need.
*. Change the GTK theme.
*. Change the Icon theme.
*. Show hide User list (names).
But remember one thing. When you change a wallpaper according to your preference, make sure the picture has the same resolution (or better) of your current screen's resolution.
And with GDM tweaker, you can choose to enable Compiz from the log-in screen (could add few more "seconds" to the booting time, I guess) or can choose to disable if you like as wel.
If you want to install it in Ubuntu 11.04, then use the below command.
sudo add-apt-repository ppa:madnessmike/madnessmikeOnce installed, you should be able to access (in classic Gnome desktop in Ubuntu 11.04) it via: "Applications" -> "System Tools" -> "GDM Tweaker".
sudo apt-get update
sudo apt-get install gdm-tweaker
Or just search for "gdm tweaker" in Unity.
Remember, don't save the images/icon themes or the GTK themes in a location that is encrypted.