What you're referring to is the boot logo
the boot splash
, that is something different).
The ability to display the boot logo is a kernel option and the image is compiled into the kernel. It can be changed using the fblogo
program, or by following the instructions at Kernel Framebuffer Logos - Troy's Linux Stuff
A Google search for framebuffer logo linux
or something similar may reveal more resources, but this should get you started. Good luck.