This is my first portrait
i hope that you can guess who is it. .
Is it you?
It´s clearly Robin Williams.
It´s not very accurate (sorry OP) however, the basic key features (his thin lips, the eyebrows, eyeshape and the nose) are really very accurate.
The shape of the head itself needs tweaking and the ears seem off. The top of his ears form one line with the top of his eyebrows. (almost)
His forehead is almost twice as high as the one of your model.
And his neck and larynge area needs to be older. His face tells his age, his neck does not. (on your model)
IMO you cought his receiding hairline very good.
His eyes are good too, but they need to be a bit smaller. They are too wide, Robins´ eyes are rounder.
Oh, here´s a nice reference that meets your models POV:
I know its finished projects, however, i would tweak it again, maybe do some texturing or use a good skinshader, this model is on the way to get photorealistic work with some efford i guess.
hth
I totally agree with arexma, especially regarding forehead and eyes.
Make the forehead higher and it will already look more like Robin Williams
About the details arexma, you are rigth and eyes were the worst problem, ill take an hour or two to refine
some things and the next post will be at focus critic first.
How did you make the hair, or rather, what are your material settings for the hair?
That’s awesome! Really great work. 
Salute your observation
well i tried these days to correct the model and textures, but I’m not entirely happy with the result, here you can see, however with this render I learn how to manage hair, projection paint and a few tricks to texture develop, a few more things about composition(i had to wacth a few tutos) so a am very happy with the prosses.
As you said arexma this is a finished project and has accomplish the objective, help me to learn a little bit more.
Next render Ill post it in the focus critic to be assisted during the prosses.
DrRobot: about the hair, is the particle hair in strand mode, the material has a ramp for the alpha, mapped in to strand mode too, and was modified using the strand properties of the material, head hair are separated from eyebrouns and eyelashes.
Here is the blend file, use it as you please, but dont mention anything about using the RGB Difuse color as Bump and Spec, I know that that is not rigth i should be done maps for each channel. . . .:o
(to download the file check under the size, webmoney, two options to the rigth says free)
http://up-file.com/download/01084c3e271dd7c8e460c47ca98c14bc7
Thanks for comment and critic, every point of view, critic and advice are always welcome.
Robin has a very flexible face, which is hard in CG. Looking at that reference, his head is slightly tipped away from you, and his jaw is slightly further down on his right hand hide. While, in theory, you should be able to do a straight-on portrait, adding flexibility will make it look more like him.
Also, compare bottom lips.
And for the record, I also recognised it.