I've just commited a rough first version of a new "cloth" material, using a BRDF from "Specular Reflection from Woven Cloth"
by Irawan and Marschner, ACM Transactions on Graphics 31:1, Jan. 2012. More details can be found in Irawans PhD thesis "Appearance of Woven Cloth"
It is largely based on code from Mitsuba renderer by Wenzel Jakob (used by permission), which again is based on code from Piti Irawan (used by permission).
Attached is the scene I've used for testing - look into the lxm file for how to use the material. The u and v stuff controls the scale of the weave - and yes,
the object needs to have u and v coordinates (either implicitly or explicitly).
There is something fishy about the specular component of the brdf as it tends to blow up here and there, which leads to fireflies.
I'm will into it as soon as I find some more time, but help is of course welcome. I probably made some silly mistake in porting it to lux.