Is it even possible? which files are involved?

I think it won't get that shiny, because the bitmap is using 256 colors, correct me if I'm wrong..

Yup, it's possible.
On a PowerPC Mac, anyway.
Just borrow the boot image off the aTV and use this program to make a new BootX
http://www.shadowlab.org/Software/software.php?sign=ImBX
This only works on PPC.

Looks like for once the older Macs have got the snazzy bootloaders

Your apple to change the image on the darwin bootloader, but no such high quality pictures at the moment

http://www.dribin.org/dave/blog/archives/2...ot_image_intel/

Well it seem possible if the image is smaller than 1,376 bytes compressed with RLE. Is there a picture of the logo somewhere?

thats for boot.efi, im talking bout hackintoshes