First day of class? Ask students to write a series of questions that could be applied to this (or other) photograph. (What happens right after this moment? What is someone in particular doing/thinking? And so on….) Pass around the questions. Write a poem based on these.
This could work as a fairly brief in-class writing that students can finish later, or discuss in their online class forum.
A useful discussion for later. Does the finished poem or story reflect the original questions? Why or why not? Is this important? (See Frank O’Hara’s “Why I Am Not a Painter” http://www.poets.org/viewmedia.php/prmMID/20422).