PiBox

1. Create PPM image from psplash image (src/logo/miot-small.png)
2. Convert to 224: ppmquant 224 miot-small.ppm > miot-small_224.ppm
3. Rename to logo_custom_clut224.ppm
4. Copy to <kernel_source>/drivers/video/logo/
5. Enable in kernel: Device Drivers->Graphics support->Bootup logo->Custom 224-color Linux log
6. Build kernel

The miot-small_224.ppm should go in the src/kernel directory, with a symlink to logo_custom_clut224.ppm.
Then the build should copy this in as part of the -init target dependencies.
Don't forget to save the kernel config after updating it!

Note that it's possible this won't work if I've moved console=tty3 instead of console=tty0. I won't know till I try it.

See https://developer.toradex.com/knowledge-base/splash-screen-linux