No pictures, but I have a rack on the back of all my bicycles (I know, the shame of a total 'rookie' move) and I can clip a light onto the rear of those racks. I also have a tool bag I mount on the racks (I swap it between bikes as needed) that can accept a clip-on light. Racks are a mix of both seatpost racks and braze-on attached racks.
And to answer the question before any ride I may be on with anyone: NO I WILL NOT CARRY YOUR EXTRA GEAR OR CLOTHING ON MY RACK. QUIT BEING SO IMAGE CONSCIOUS AND GET YOUR OWN RACK