Since Ubuntu 9.10,there’s no “login window” option in System menu to change login window icons,background.To change login appearance in Ubuntu 9.10 and higher version becomes inconvenient.Fortunately,there are two GUI tools I found that could instead to accomplish this task.

1.GDM2Setup,a GUI tool designed to configure login screen behavior.It can be installed by following commands in Applications->Accessories->Terminal

sudo add-apt-repository ppa:gdm2setup/gdm2setup
sudo apt-get update
sudo apt-get install python-gdm2setup

launch GDM2Setup from System->Administration->Login Screen(GDM2Setup),change Login screen background in Wallpaper tab,GTK theme and icons theme in Decoration tab,more options in General tab.

2.Ubuntu Tweak,a great tool provides many useful desktop and system options that the default desktop environment doesn’t provide.Ubuntu Tweak can be installed by following commands in terminal:

sudo add-apt-repository ppa:tualatrix/ppa
sudo apt-get update
sudo apt-get install ubuntu-tweak

launch Ubuntu Tweak in Applications->System Tools menu.In its “Login Settings” tab,click “Unlock” and you can easily change login screen logo and background: