Is it legal to ask a job applicant for a photo prior to an interview?

If the job is casting actors for a performance, it would be.  Otherwise, the last thing a prospective employer wants is pictures of people before making the hiring decision.  Most, if not all, reputable employers would send back a resume, etc., if there were a picture.  This is so hard to believe that I am curious as to why this is being asked.  A plaintiff's employment lawyer would have a field day with a discrimination case.  I am salivating. Maybe I should get admitted to practice in Mo.  Seriously, there has to be something I am missing.