After doing some searching and browsing files in Sailfish, I think that the initlogo.rle could the boot logo, found in root. But cos I'm total noob, I won't try to mess with it :P
Tried to replace this file with my own one and reboot, but it still show the standard Jolla logo on the boot...
It's not enough to just replace this file...
Shutdown logo is easy to replace, but you will be having hard time replacing boot logo, as its builtin inside bootloader, so there is no easy way to change it.
So we need to insert custom RLE into the boot image. There's plenty of discussion online of people doing this for Android - how different is it likely to be for Sailfish?
maybe it's not a problem to insert the rle file to boot image, but from what I understand we need flash this new boot image and not just put it in the file system. I don't know if it possible for normal user in the current stage (no flash tools)..