Nice studies lionarmor! It would be easier to give you critiques if you put the photos you're referencing next to the studies. I also think you should resize the studies so we can see the whole image, 700-900 pixels on the longer side is usually good.
Do you have James Gurney's Color and Light? it's a great resource for learning about...well color and light XD
I think you may want to try experimenting with different texture brushes, maybe mid way switch to a texture brush, after that go over it, soften and blend it in with a normal rounded brush...right now the skins look a tad pasticky. This method might help you out. Also, stronger tones will help to sell the form and planes of the face.
Good start! lots of good depth of shadow in your paintings. I would say, be careful about using pictures like in#7 at the moment, as it doesn't really describe form, light or colour very well. Keep it up!