So, found some tartan wool on e-bay for a steal of a bargain, and Shadow ordered it for me. It looks good, though it's not the colors I had hoped for. It's black on red, a variant of the Leslie family tartan. (Not that that matters, since family-related tartans is strictly 17th century and later anyhow, but it's fun to pay attention to it, anyway.) Shadow was pleased, because it's basicly House-colors for Serpents' Coil. (Which has now at least a working banner design, although it might evolve and improve before we settle for good.)
Here's the kilt fabric:
And here's the banner design: