Traditionally, you'd probably use silk brocade, but that's cumbersome, expensive, and probably hard to find. In the photos, the outer robe looks like it's made of two layers, a sheer embroidered fabric over something heavier.
For my madoushi costume, which is similar in overall appearance, I actually used a fantasy-Renaissance pattern, think Lord of the Rings style. It requires quite a bit of modification, though. I think traditional Chinese sleeves are completely straight, just really, really wide; you might be able to freehand a pattern.