###############################
### THEME FOR THE MAIN MENU ###
###############################

1- Copy the folder of the theme in /boot/grub/themes

2- Modify the file /etc/default/grub by adding these lines:

LANG=fr_FR
LANGUAGE=fr_FR
GRUB_BACKGROUND="theFileYouWantAsBackgroundAsTerminalInTheTheme"    # if you comment this variable, grub will look for /usr/share/images/desktop-base/desktop-grub.png image instead
GRUB_THEME="/boot/grub/themes/Crunchy-1024/theme-potatoes.txt"

fr_FR is an example as a locale

3- update grub

sudo update-grub

#############################################
### IF THE THEME IS NOT FOR THE MAIN MENU ###
#############################################

If you have a menu entry like this:
menuentry "...       Menu on /dev/sda2" {
	set root=(hd0,2)
	configfile /boot/grub/grub.cfg
}

2 cases : 	* if it hasn't any theme, the current theme will occur
			* if it has an active theme, its theme will be activated
	

but if you have:
menuentry ">>> 'live' distros launched from their iso" {
	set root=(hd0,10)
	configfile /isos/00_isoboot.cfg
}

It won't have a 'sudo update-grub' to had useful lines in the config file.

So, you'll have to had the 'loadfont' lines, the terminal background image and the theme in it.

loadfont /isos/themes/Crunchy-1024/PoiretOne_normal.pf2
loadfont /isos/themes/Crunchy-1024/PoiretOne_title.pf2
background_image /isos/themes/Crunchy-ubuntu/0_commun/term_borders_c.png

theme=/isos/themes/Crunchy-1024/theme-potatoes.txt

If you want a default menu to be launched automaticaly, you can add:

set default=2
set timeout=8
