GRUB 2 Splash Images on Ubuntu

Here is how you can get a nice background image for GRUB boot menu.
First, install the "grub2-splashimages" package:

sudo apt-get install grub2-splashimages

Then edit /etc/default/grub and add the following line

GRUB_BACKGROUND=/usr/share/images/grub/yourImage.png

Also, make sure that GRUB is loaded in the same resolution as the image

GRUB_GFXMODE=1680x1050

...and that's it. Update GRUB

sudo update-grub

and restart to see the results.