There are many methods to change the “login Background image” in in Linux Mint/Ubuntu. Lets see the easiest method. 🙂
The simplest method is download the “ubuntu-tweak” and configure Login Settings.
Then access it through Applications → System Tools → Ubuntu Tweak
When Ubuntu tweak opens go to login settings and click unlock and enter your password when prompted.
Click the button to change the login background:
That’s All. Enjoy it !!! 😛