Grub menu how to costumize

On dual boot you have the black screen with white letters, but you can change this here in this page you can change everything for mete or needs, like time to boot the default OS normally 10sec the colors of the letters and a wallpaper "Grub splash menu", i have made a few so you can used one if you like from here on my art gallery. This is the look of the splash menu on grub