Expressive Drapery

This drawing by J.W. West from the Magazine of Art in 1895 shows the expressive power of classical drapery. 

Small halflock folds contrast with long pipe folds, which accentuate the gesture of the leaning woman. Some folds lie inert on the ground while others spiral and bunch up.

This sort of drawing is only possible if you observe real people in real costumes enough to get the feeling of what kinds of drapery effects are possible. At that point an experienced pen and ink artist can invent drapery from the imagination, but it never hurts to have a model or a lay figure for reference.