After I made an appointment for an interview they sent me a list of things I needed to submit and a photo was definitely on that list. They want you to mail it to them, not bring it with you at the interview.
right, after you get your interview offer, you call and set the date. then they'll tell you to mail the technical form from your interview offer letter, plus a photo before the interview. sorry for the misleading reply.
You should probably submit a photo before the interview (although they will give out interviews without photo submission I presume). They use the photo during the interviews so that your interviewer can pick you out...i.e. the applicants walk into the lobby where interviewers are waiting and your interviewer will come up to you and recognize you.