I have an article posted on "Guide to Literary Agents" on the topic of appearance. I wrote it a long while ago but I guess I feel the same way. The very first book I published I had my photo on the back but I've never done it again. If my editor asked me I'd have my photo posted but no one has really asked. There isn't enough room because they'd rather advertise my other books on the flap. I will say that thanks to the prednisone I'm on my face gets puffy sometimes and that makes me insecure so I'd have to use a photo pre-prednisone.
What I question in my article is does appearance matter? Does it change how you feel about the book or the author? Is it better to not have a photo? I always think it's funny to see Shell Silverstein's photos because he looks a little scary. Then there are the photos that are clearly when the author was like 20 years younger.
Check out my article and make a comment. A free book goes to a random commenter! Of course you can always comment here as well.