The quality of the texture maps you use can be a major factor. As an example of this: the other day, I bought one of Handspan Studios items (Audrey) in the Renderosity Store, mainly for the sake of the nice face & texture they had done for Zygote's Vicky. I don't intend to give a plug for Handspan, but they do terrific work & their prices are dirt cheap. The quality of the rendering of a closeup of Audrey's face, even at a relatively low resolution (less than 1000x1000) was really breathtaking, compared to a few other texture maps that I use on a regular basis, including my own. Irises, eyelids, etc. can look almost photographic using a good quality texture map such as this. As for camera focal length: be sure to use a long focal length when rendering, comparable to what you would use with a good camera when doing portraiture work, i.e., at least 90 mm, or even 110 mm. This will help prevent distortion of facial features if you're doing a head/shoulders shot. Also, be sure your model is properly oriented on the Y axis to your lights so that the facial features become nicely "sculpted" by the light. Having your model spun around the wrong way in relation to the main lights will result in inferior renderings.