In this picture two light rigs are quickly swapped. The light rigs (courtesy of Christian Bloch's sIBL) are based on lights and Backdrop Radiosity (for ambient), which is being driven by the Texture Environment plugin. In this workflow, each light rig's Texture Environment settings are saved, and the key lights from the two rigs are grouped separately. When a pass is created, the user associates the desired Texture Environment settings that were saved, and assigns the particular group of lights that go together with that Environment.