Do you mean "subdued lighting"? If so thats a tough one to have to do an exam on. Things that I think of when those words are put together are a neon sign thats a word with like one letter flickering, sunsets, looking down into the depths of the ocean, starlight, a candle, different coloured rooms e.g a red room or a green room where photos are developed.
Sorry if this is no help at all, especially as its your final peice im sure you'd feel more comfortable with an idea you've come up with yourself just keep mindmapping ideas till you've got one you like.