Fedora: Set background for grub2 boot
In file /etc/default/grub
- Possibly increase the timeout so you can see the background for longer
- Comment out GRUB_TERMINAL_OUTPUT
- Add GRUB_BACKGROUND with quotes and valid path in /boot
The file image in this example comes with Fedora grub2.
If you're going to use your own, make sure its 8-bit (256 colors).
GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
grub2-mkconfig -o /boot/grub2/grub.cfg
Make sure it says it found your background.
Commenting out GRUB_TERMINAL_OUTPUT made it find it for me.
Reboot to see your creation: