The bootlogo can be any size with a maximum of 720 x 1280.
When it's smaller than 720 x 1280, it is automatically centered and the background takes the color of the first pixel.
The process is to create a landscape bootlogo and then rotate it 90 degrees counterclockwise.
Lastly, the supported format is 32-bit (ARGB) BMP. Classic 24-bit (RGB) BMPs are not supported for performance reasons.
If a boot entry specifies a custom logo path (logopath=), this one will be loaded.
If the above is not found or the format is not correct, it will try to load bootloader/bootlogo.bmp.
If this is not found, the default hekate logo will be used.
(bootloader/bootlogo.bmp is basically like a global bootlogo.)