I want to change the login screen background and grub bootloader.

Hi, there. can anyone plz tell how could i can change the login background in latest kali linux and how can i change the image of grub bootloader image which i tried to change but i automatically changed to blue color instead of the image i had chosen and after i run uodate-grub command ?

Login screen can be changed at settings. Grub screen dont know

I had tried all ways to change the login screen background.

I want to change the greyish login background with some picture.