Nice to see a thread on train interiors, which always seem very neglected compared to the exteriors! I find it jarring that so many heritage lines use non-standard fabrics now for refurbs. You wouldn't paint the exterior in any old made-up ivery, so why is the interior any different? I am sure getting replica fabrics made isn't cheap though.
Moquette is very expensive to purchase. I was involved in a project that needed some new for squab panels etc. We had to buy multiple times more than we needed and sell most of it on to other groups.
There should be a decent market for the more popular, authentic designs though.