One of the reasons for the 'flat' feeling, is that there doesn't seem to be a direction for the shadows on the robe to be coming from. The base three-dimension figure has a distinct light source from 'above' (check the shadows on the face, chin, hands, and shepard's crook), but the folds of the robe are equally shaded from two sides (right and left) which contradicts the 3D parts. As Chuck said, there needs to be more shading under the robe's edges..onto the elbows, wrists and feet. It is tough trying to shade vertical folds with an overhead light source...would've been easier if the light was off to one side or the other.

RosemaryR
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"This...this is magnificent!"
"Oh, yeah. Ooooo. Aaaaah. That's how it starts.
Then, later, there's ...running. And....screaming."