As a members' choice Achilles put his own photo on the front page on his own web site.
Is it really Members' choice or .......
   

how is it defined?

Members Choice is based on the number of comments that an image receives from different users. It is probably generated automatically. I suspect that his images get lots of comments because members will ask him questions by posting a comment on one of his images instead of trying to email him via admin or support. He has frequently suggested that one leave a comment on any of his images if they want to contact him. He does respond quickly if you do. I don't think anything is rigged and I would bet few people even pay attention to this area of the Stats & Community page.

Agreed - I think it is meant to be the images people are commenting on and talking about.  It is probably a bit skewed now that automated e-mails all go onto your most recent upload.  If you don't upload much, and have lots of favorites who post blogs, you'll probably get into the 'members choice' !