I am back this time with a small trick. Many of us do not like the old background in GRUB BOOT LOADER, you might be using kali linux or any other linux and using GRUB BOOT LOADER then this is for you.
First of all,open root directory find a folder named "boot"
Inside the boot folder , find another folder named "grub"
Now get into the grub folder and place the background you want.
GRUB 2 can use PNG, JPG/JPEG and TGA images for the background.
However JPG/JPEG must be 8-bit (256 color).
And Images should be non-indexed, RGB
Now we need to update the grub.cfg file.To do this open the terminal and type this command "update-grub".
Now reboot to see the changes you have made.