Here you can see I've started in on the refrigerator Notice how I've established a strong light source with the torso and head of my robot. I will carry that through the rest of the piece which will help tie all the elements together and put them in a believable space.

Also, notice that I tend to use mysterious fill lights of a complimentary color... I couldn't tell you where the lights coming from but as long as it looks good I don't think it much matters.