Hello solala,
Thank you for your input, and you were spot on. File size and header info are exactly the same as the pictures used by Fortis. If I rename the unpacked .gam picture to duckbox.Booting.gam and gzip it, then add the .gz as user data (partition type 9) to the fup arguments, flash the .ird, then the Linux and Atemio logos (plus the text Titanit) are shown on power on. Can you enlighten me on how to create my own .gam pictures?
Meanwhile I have added support for the bootpicture to the flash environment: if X/cdk/root/bootscreen/bootscreen.gz is found, that file is used as the bootpicture file.
Regards,
Audioniek.