Thinking back to the first day of class, I remembered the photo Professor Koss showed us online. It was a photo of a prisoner of war, taken by the enemy to show the American people that they were treating their captives well. However, the prisoner was giving the middle finger to the camera, clearly showcasing his resistance to his captors. Though the enemies didn't understand the meaning of the hand signal, the American people did, and they understood that the prisoners were not being treated well and were not giving in to their captors torment.
Similarly, I was watching a show called Prison Break, and the plot involves the capture of two people for the purpose of blackmail towards the main character. The main character won't do what the captors want until he sees a picture of them alive and well, so the captors agree. The picture he receives shows them subtly pointing to a location and time on a newspaper, hinting at where they're being held captive. The main character is able to locate them and attempts to rescue them, but unfortunately fails.
In both cases, the prisoners are subtly hinting something to their audience in an attempt to receive help in some way.