Kyle,
Katakiri-bori subject matter finds its influences from many sources, Itcho being a major one. You are correct about the importance of identifying source material, a familiarity with the Japanese visual arts is crucial to the understanding of tosogu on all levels, without it you are seeing with one eye. BTW, don't get hung up on "originality" as, in many ways, western constructs do not apply here.
Cheers,
-S-
p.s.-considering the kao (see the two posts prior to yours), Furukawa is not a horse in this race.