The file `large-penguin.mbicon' (mbicon == MultiBoot Icon) is an icon
that will replace the disk-icon-with-small-penguin-badge in the
OpenFirmware multi-boot screen (hold down option on AGP G4s and
iBooks).  In order to use this copy an uncompressed copy somewhere,
and add `icon=/path/to/large-penguin.mbicon' or whatever to
/etc/yaboot.conf and run ybin.  You can add other types of icons so
long as you put the proper bootinfo tags around them.

This is unsupported and you are on your own.
