I love velvet skirts (and velvet in general) but they're so hard to pull off. I have a floor length one with a slit up to the thighs and it's the most unflattering item of clothes I've ever owned. I think you need to have very narrow hips and long legs to make this look nice.
Most of the ones you posted are high waisted, though. I wonder if that makes a difference? I really love the color of the one at Balmain