You might have heard of background image in GRUB boot screen. You can change the ugly black background of GRUB using a few little steps.
1 – Press ALT + F2. Type this in the input box of the window.
gksu gedit /etc/grub.d/05_debian_theme
and press Enter Key.
The program will ask for your password. After typing the password and pressed the Enter Key a gedit window will appear. Press CTRL + F and search for WALLPAPER= after you found the word copy the location where your background image is and pate the location in quotes after the "=" like in the image shown below.
After editing the file press CTRL + S. After Saving the file press ALT + F2 again. This time type :
gksu update-grub
and press Enter Key. A Terminal window appears and will close after some time. Reboot your computer and you will see your new Background Image.