How To Create Photo For GRUB

1.Resize the picture to 640x480.
2.Reduce Colors to 13.
3.Save as xpm file and compress to .gz.

In GIMP:

1.Image->Scale Image to 640x480.
2.Image->Mode->Indexed to 13.
3.Save as xpm.
4.Create archive as .gz.
5.That's it!