Dear Nathan,
You are an artist on a roll, which is terrific to see. One of the things I like about your work is that you're really making an effort to discover what makes a face truly individual, and that you're not giving everyone the same nose, eyes, etc.
You are experimenting with different mediums and light sources, which is great. Eventually you'll discover that some light sources work better than others for certain people, and the same is true for different mediums and papers. (By the way, I think you are working very small. My suggestion is to get a bigger piece of paper and plan on making the head closer to life size. You'll be able to get more detail in there.)
Keep experimenting with natural light, artificial light, light direction (don't forget overhead light) and harsh vs. diffuse light. (I like Wendy Caporale's chapter on light in her book "Painting Children's Portraits in Pastel".)
As far as colored paper is concerned, be sure to check out the post under Drawing Critiques titled "Sally Study". There's a good discussion of the work of the French artist Pierre Paul Prudhon, who worked on a blue-gray paper, and some good photographs which show his style. If you find that you really like his work, check out this site by the artist Rebecca Alzofon:
www.art.net/~rebecca
She gives a very detailed and wonderful step by step method showing how Prudhon worked. (Thank you, Chris Saper, for showing me this site.) (And if you haven't already, check out Chris' terrific drawings which William Whitaker posted in the Unveilings section of the Forum.)
Drawing from life will help you see subtle modeling and value changes which can be very hard to find in a photograph. (Tony Ryder calls this aspect "fullness" in his book on drawing the figure in graphite. This is a great book to have in your library.) It is also a wonderful way to learn to see the relative softness or hardness of edges. A couple of ways to see value differences in drawing from life is to squint (you already knew that) or to hold a piece of red acetate in front of the subject.
Mari,
I agree with you that photos are still a very good idea. For one thing, subjects tend to move around a lot, unless they're professional models.
Photos help you find the boundaries of your subject, but working from life will help with all the subtle things that happen within the boundaries that give your paintings a sense of life. (Incidentally, I find that photos are very valuable tools for composition purposes.)
I agree that Morgan Weistling takes stunning reference photos. However, I've taken his workshop and his work from the model is equally breathtaking. (And having seen Peggy B.'s tapes and watched her work from life, she can also produce stunning work from life or from photos.) Possibly, the answer is to alternate working from life with photo work, as well as learning how to take better photos.
Michelle,
Thanks for the double chin/looking down tip, I'll use it soon.
Best regards,
Linda