Older GRUB tutorials often describe copying a splash image into legacy GRUB directories. Modern distributions generally use GRUB 2, where appearance is controlled through configuration files and optional themes.
Start with the GRUB configuration
Common settings live in /etc/default/grub. Depending on the distribution, themes may be referenced with a setting such as GRUB_THEME. After a configuration change, regenerate the GRUB configuration using the command appropriate for your distribution.
sudo update-grubOn distributions that do not provide update-grub, the equivalent is commonly a grub-mkconfig command targeting the distribution’s generated GRUB configuration file.
Be cautious with bootloader changes
Theme or background changes are cosmetic, but mistakes in bootloader configuration can still leave a system difficult to boot. Keep rescue media available and avoid overwriting generated GRUB files manually when the distribution provides a supported configuration workflow.