I really like the design and execution.
About the robes: right now, something that's really hurting the illusion that it's cloth is that the bottom corners are rounded over. Instead of being a crisp 90 degree corner like you'd expect to see on a sheet of cloth (as an example). I'm terrible with greenstuff robes, so unfortunately I can't offer an tips on fixing it.
Also, it would look even better if you built up some folds on top of the existing skirt/robe. Nothing too drastic, just a little something to give is some motion and weight.