Possible Duplicate:
Problem getting Facebook pictures via iOS
How to get user's facebook profile pic via fbconnect in my app iPhone?
Try look deeper through http://developers.facebook.com/docs/api. Here is a link to userpic:
http://graph.facebook.com/000000000/picture
Where 000000000
is an id of user logged.
UPDATE by Michael Gaylord: You can also append the type to the request to get different sized images. So your request will look something like: http://graph.facebook.com/00000000/picture?type=large for a large image. Other options are small, normal and square.