You know, it's really hard to tell - I can see a face, but it looks to me to just be the pattern of a tree trunk. It will be interesting to see what the photo analyses have to say about the photos.
I played around with this pic a lot. I kept getting the same pattern within the circle as the rest of the photo. So I really can't see what it is your seeing.To me it looks to be a case of matrixing, But then again I wasn't there so it's hard to say.