grub-bgrt theme: A theme for GRUB2 which uses your system’s UEFI logo (aka BGRT).
I expect this will be popular.
This old blog post is still a commonly-accessed blog post, it seems people like to hack BGRT images on their sysetms:
https://firmwaresecurity.com/2016/05/21/hackbgrt-changes-windows-boot-logo-on-uefi-systems/
OEMs, consider making this a user feature via your boot menu.
See-also:
https://docs.microsoft.com/en-us/windows-hardware/drivers/bringup/boot-screen-components
https://blog.fpmurphy.com/2015/07/access-bsrt-information-and-boot-logo-from-uefi-shell.html
Firmware Security 