A picture from the 1974 adaption of Murder on the Orient Express. Films are a great source of motives, both in terms of scenery and facial expressions, but in particular of interaction between people. While I can draw a single expressive figure, I often find that quite difficult to draw to or more people interacting. They often end up not quite looking each other in the face or somehow not being together though there are on the same page. Also, when you have use a film as reference instead of a picture, you feel the mood and the tension between the characters better and I think it shows.
An extension of this exercise could be to take an entire scene and convert it to a comic book page of 4-6 picture.