I'm not sure if the picture is grainy or the model. From what I can see the wash kinda stuck flat areas instead of pooling in the shadows, which is fine if you are going for a dirty/grimy look. If so I would recommend hitting it with some weathering powders and get some dirt and dust on him.
The
OSL needs more of a contrast and a focal point. Also the
OSL should reflect off of the metal of the Necron to give it a more realistic look. Don't feel bad
OSL aint easy, Heck I haven't even gotten it to anywhere near what I would consider good.
Hope that helps.
Here is a picture to illustrate what I mean by the Necron reflecting the light of the object. (Found this on google).