One of the most interesting and effective interpretations of this exercise that I have marked involved a common theme of faces. The faces of statues to be exact. Each was made out of a differently coloured material - one white, one grey and one black. The three shots fulfilled the needs of the exercise brilliantly, were attractive in their own right and also showed that the student had really thought about how the shots would fit together. That said, the brief does not mention anything about creating a common theme. Personally I do think it's a neat solution though - one that makes it easier to find your three objects.