I think my unlikely favourite, for the sense of tranquility, is Portrait of Einstein, by Yousuf Karsh (1948, Princeton, New Jersey). The AIDS Memorial Quilt by Paul Margolies (October 11, 1996, Washington, D.C.) was... hard to describe. I guess it stays in my mind, being the last image in the collection, and it having taken me so long to finish going through the book, which I read from front to end.