Another way of finding what may be the only photograph of a relative is from a passport application. Ancestry.com features applications from 1795-1925, though the collection is not complete. The earlier applications contain a physical description, while the later applications may contain that coveted photograph.
I found a picture of Alexander Lutter, one of the Chicago Lutters that I research. This is from his application dated 2 July 1920.
I wouldn't say that he resembles my known Lutters of the time period, but the photo is still wonderful to have.