Do the same activity, but this time using two pictures: one is the first shot in your film and the other is the last shot. What is the story that links them?
Start with a picture featuring two or three people. Start by creating a 'tableau' - actors stand frozen in the positions of the people in the picture. Set up a camcorder on wide shot and start filming. The actors 'come to life' and improvise from the starting position. Use what you have filmed as the basis for developing a script.