The faceted mirrors add visual impact, create interest with their distorted reflections, and subtly echoe the angles in the cut of the garments. A clever touch, I must say. Another brilliant use of mirrors in a performance-like presentation is Alexander Mcqueen's Spring/ Summer 2001 collection, which is nothing short of hypnotizing. Unfortunately, I can't find images of good quality for that collection, but there is a Youtube video that you can check out.
1 hour ago