APA Style Citation for Pictures
Option 1: Citation as part of caption
Option 2: Citation placed in References Page
Crocodile [Image] (2005). Everglades NPS. R. Cammauf. Retrieved on 2015, October 23 from https://www.flickr.com/ (CC Public Domain Mark 1.0.)
Writing tip: If picture is used in a presentation such as a Powerpoint Slide then you can put the citation in the notes section to avoid clutter.