Hang a curtain rod draped with sheer curtains (or fabric) at headboard height, behind the bed, then add some white holiday lights behind the fabric and across the rod.--- maybe just a string of lights over the headboard :)
Small mirror tiles glued to fishing line with lights behind. This is fantastic.Such a cool easy idea. Would be great in a dorm room. Those after Christmas sales are perfect time to get a light set cheap for this DIY project!