Sure, they could have chosen a less flattering picture, but they didn't need to. The picture humanizes him, and reminds us that looks aren't everything. I was deeply affected by the Marathon bombing, and still feel the echoes of it. However, it behooves me and others like me to remember that there isn't a 'face of evil', per se.
Plus, it does touch on the fact that he is innocent until and unless the prosecution can prove his guilt.