I love the portraits and the simple design; however, I did see some things that could be corrected. The header isn't exactly in line with the link bar. If you corrected it, I think it would look a lot neater. You could also darken the header text and clear up the image. Right now the design is nice, but I can barely read the text. Furthermore, it looks a bit grainy, as though it weren't optimized for the website.
The artist's work is very nice, maybe you could put an example on the main page to draw other people in to look at her work. The whole point of the site is to showcase her artwork, after all. Other than that, though, the site was very easy to navigate and looked very professional. Good job!