You certainly know the person who writes your blog. But do your readers know him / her? Your blog doesn't need a full auto-biography about you, the author of the stories. However, a few sentences are good for readers as writings that are simply anonymous don't hold much water for people if they don't know anything about the author. Moreover, people want to know your credentials and see if they should be reading what you write. Will people believe something about deli meats that they read from someone who works for a baseball team? (I used deli because I work in one)
On that same level, a picture is helpful, for as one blog writer put it: "It offers a more personable impression of the author. You enhance your credibility by the simple fact that you're not trying to hide. Also, users relate more easily to somebody they've seen."
Good luck blogging!
P.S. >> To the upper left of this post, you might see something saying "Get Email Updates" etc. This is a free service that allows users to sign up with an email adress and get updates on new posts in your blog. This is yet another way to help bring back readers... Sign up for my blog updates today! All email addresses are kept private.