fulloflead,
the choice of menuki, both design and materials, is not arbitrary for the Japanese. These things must be chosen very carefully, according to functional requirements and a very rich, old, and well adhered to aesthetic code, if you will. WHen someone like Snody puts a menuki on the handle of his blade, it probably was chosen for its meaning. It would be great to send him an e-mail and ask how he chooses his menuki for his blades.
Typically on Japanese swords there are several "points of ornamentation". The color and decoration of the saya (scabbard), the tsuba (guard), the way the tsuka (handle) is wrapped, the menuki, the fuchi and kashira (end caps for handle), the seppa (washers), and on, and on. A katana with Mount Fuji menuki, a crab designed tsuba, bright red saya, copper seppa, a brass fuchi with a dragon design on it and an iron kashira with dogs on it would look interesting to many newbies to japanese swords, but ti really would be fugly! The colors don't match, the designs are all over the place, the materials don't even blend well together, etc. I can't think of any good fittings books off hand (Robert?) but go to your libraries and check out every book you can that has japanese blades in them. A lot of unviersities have books on Japanese art which have blades in them too, so check all sources! The more you read, the more you'll be fascinated and the more you'll want to learn. Also, send to Fred Lohman for his catalog. There are all kinds of great sword fittings in it too look at.