GRUB splashscreen format?

[Mike Sowka]

Hello,
I was hoping someone coule inform me on the format of the GRUB 
splashscreen. I tried "gimp"ing my favorite background to xpm then 
gziping... but trying the large 1.4M, ??? wrong format ???, 
splash.xpm.gz really messed up my system. It would just keep 
rebooting..., grub clearly not liking SOMETHING! :( After rescueing my 
systems back to the original splash screen everything is back to 
normal... but I'm hoping someone on this list may be able to inform me 
on the required format for the splash screen so I can, in the true 
nature of a linux lover, customize! :)
Thanx,
BTW (in case it's needed, which I doubt) my system specs are:
P3 533 on a VIA 133
TNT2 card and RH7.2 with custom kernel (2.4.13)

Mike