The GIMP image editor is one application which can edit images to conform to the GRUB 2 standards. Since most of the time you will not want to limit yourself to 256 colors (which is totally yesteryear) you will probably find PNG much preferable. Else you will get errors saying "Too many Huffman tables".
Grub2 themes girl how to#
This page provides information on how to add a background image, change font colors and resolutions on the GRUB 2 menu without using a theme. GRUB 2's splash image/background capability is greatly enhanced over its predecessor, GRUB 0.97.