A day before christmas

I'd suggest shading and tinting using the pen tool in photoshop; select areas you want to be dark and trace around them, then fill an empty layer above the drawing with black and reduce the opacity to, say, 10%.
Do the same with the tint but you might want it a couple percent higher, or make the shade more transparent by a few percent.

The shading on this is really bad, that's it's major weakness; never use burn and dodge for shading and tint because it's really "gimmicky" and doesn't look very good at all when you're not very skilled with it.