We should find a way to replace the banner image used in the graphical
version of the debian installer.  The image used by g-i is
/usr/share/graphics/logo_debian.png from the rootskel-gtk package.
It  is a PNG image data, 800 x 75, 8-bit/color RGBA, non-interlaced.

It is unknown how to properly replace it in a custom debian distribution.
Perhaps we need to make our own g-i boot images to make it happen.

An idea is to modify debian-cd to append a compressed cpio archive with
this replacement file to the initrd.gz file used when booting g-i.  It
will then replace the original file when the initrd is unpackaged into
memory.
