I do not know if this will help, as I am using Red Hat 8.0.
My splash image is at /boot/grub/splash.xpm.gz
Assuming of course that you mean the image that comes up when you are asking by GRUB what you would like to boot into.
I'm currently looking for ways to change it myself. After playing with it for a while, all I ever managed to do was turn the boot splash screen a yellow and orange striped pattern. It was supposed to be a giant penguin, but hey, can't win them all.