How to Install background image for grub in linux Mint & Ubuntu

Try Following  Steps

1. open  Terminal
2. type  sudo apt-get install grub2-splashimages

3 . after installing the above check  folder  /usr/share/images/grub/

4. you can add images to this folder by pasting images to this folder
                        for changing the permissions of the folder 
5. after this type sudo gedit /etc/grub.d/05_debian_theme in terminal

6. find the line set_background_image "/usr/share/images/desktop-base/desktop-grub.png" 
 you can use Cntrl + F to find the line 

7. change the desktop-grub.png to the filename you like and save
8.  then type update-grub in the terminal

9. restart the system ,now you can see your custamised grub background 

for changing again background image  edit the file  /boot/grub/grub.cfg