I love this advice so much, keeping this in mind every time I sculpt. I admit I have a lot of difficulties with fabric and materials, it's pretty hard to make them look believable. I'm thinking to learn MD sooner or later to apply to my work. The funny thing is Arishok was one of my earliest sculpt, I think I'm digressing…
All the 3d characters are pretty good. Main weakness that jumps out to me is material definition and I guess what you might call "secondary forms." Materials all feel like plastic across most of the characters. I'd aim for a stronger distinction between cloth, skin, metal, leathers, etc. A good piece of advice I once read…