I really like the grim, earthy colors and subtle lighting. Rather than increasing the exaggeration already apparent in the linework, it complements it with a feeling of realism. They also create an appropriately grim, brooding atmosphere for these shady characters. Excellent work!
Sorry mate, I meant modelling in the painting sense, as in creating the volume of the arm, doing the light and shade. Grainy brushes and dissolve brushes, I'll have to spend some time fiddling with that, it's a wicked result you've got.