Pretty good proportions and general anatomy. The shading looks very dirty, however. I wouldn't use a black airbrush to shade. What I do for my art is pick a colour like purple, and do a multiply layer over the colouring. You also want to establish a light source, because what you're doing right now is called pillow shading, where you just put shading wherever you can think to add it. I don't know what program you use, but a lot of software use stabilizers for inking. I'd try to use those as well as add some pen pressure (unless you're using a mouse, in which case, not much you can do.)
Not bad at all. I like the solemn warlike feel to it.