Hello, all. I've done something I should have a long time ago: I've
merged gfxmenu documentation in official manual. It's available under
http://www.gnu.org/software/grub/manual/html_node/Theme-file-format.html#Theme-file-format.
Unfortunately it uses the following images:
Box_slice_example_terminal.png, Theme_boot_menu.png,
Theme_circular_progress.png, Theme_progress_bar_filled.png,
Theme_progress_bar.png
It also refers to an example theme.
Legal status of these images and theme ranges from unclear to unusable
(we can't use Ubuntu logo). So these items were incorporated in GRUB.
@Colin: can you tell which of the items are actualy ok? Beware that even
using non-free font like Helvetica found in some of your themes or
non-free background makes it unsuitable for trunk

Is anybody interested in supplying a free replacement?

-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko