I have just found this website :-
http://www.makehuman.org/ who have software to produce a 3d figure, you start with a basic figure and can tweak the features etc to alter the model to resemble whoever you want, its quite easy and versatile though the clothing choices can be somewhat limited. I had a go to try and change the features to match those of the skipper of the boat I am modelling, here is a screenshot of the resulting stl file. plus a photo of the face I was trying to model