Easily change your login background with ‘Simple LightDM Manager’.
The default login background image matches the default Ubuntu wallpaper. Chances are you’ve changed the latter, so why not the former?
This is easy to do by installing ‘Simple LightDM Manager’ – a small app that lets you choose and set a different image as the login window background.
Download it here
read more about its features here
You can change the background also manually by opening a erminal. (Dash > Type ‘Terminal’)
Enter the following command oh-so carefully: -
gksu gedit /etc/lightdm/unity-greeter.conf
In the Text Editor window that opens make sure you DO NOT edit anything bar the line highlighted in the screenshot below: -
Edit this path to lead exactly to the location of the image you wish to use. Remember – it must end in a image format (.jpg, .png, etc)
Hit save, close the text editor window and log out of your session – You’ll now see your custom LightDM background in use!