grub spash image

just add the image file to the /grub directory in .xpm.gz format
the default name should be splash.xpm.gz
then rebuild grub image

you can get ready-to-use images anywhere ... eg: here

example commands:

cd /boot/grub
wget http://ubuntuforums.org/attachment.php?attachmentid=17670&d=1161005960
update-grub

that's it :)