Thanks for your reply.
I have been able to create the ppm file.
Unfortunately I do not use Toradex. I am using the default Beaglebone Black debian image.
Where do I have to copy the ppm file to? And how do I rebuild the kernel?
My approach would be to replace the lunux tux ppm file in /kernel/drivers/video/logo, but I can’t find this folder on my Beaglebone. I was looking under /lib/modules/4.19.94-ti-r64/kernel/video, but the logo folder does not exist in here.
Could you point me into the right direction?