I don't want to repeat myself with other complimets (I did it in PM too), so let me express just one thought about human figures and renderings. Take it as just my personal reflection on this subject, with no intent to compete with (or discuss) your hands-on experience in this field.
I believe that a rendering is a great way of communicating the design intent. But imho it should stop at some point before reaching the look of a real-world photography. I think it should be a form of 3D artistic rappresentation of a designed object and a person looking at it should be aware that he (she) is in front of an artistic rappresentation - not of a picture of the real object. I prefer a rendering which leaves some details uncomplete or non-perfect, because unsaid things stimulate our imagination and our curiosity much more than a picture in which every detail is shown and nothing more can be added.
So please let me disagree with you when you say that it is necessary to create 3D human figures look "believable".

Why not, for example, using blatantly fake 2D human figures and giving the whole thing that touch of artistic surreality which could stimulate people's fancy? Why not taking it to the level of an artwork, instead of trying to make a perfect fake photography?
I think that Japanese cartoonists have reached a near-perfection of that concept - just an example here:
http://www.designchronicle.com/memento/archives/the_uncanny_valley.html
I know it may be the opposite of what your client had asked you to do, but if you present him a work that goes out of line in some surprising direction he might change his mind too...
P.S.
By the way, this Chianti red wine I'm drinking right now is a real artwork.