There is a wide array of hardware available to help hang a heavy picture on drywall. One gadget I really like is the Monkey Hook, an easy-to-install wall hanger that supports art weighing up to 50 pounds and can be doubled up for even heavier pieces. It was created with both residential and commercial drywall in mind, and designed to work in wall locations where there is no wall stud to latch into.
The Monkey Hook looks is a hook shaped piece of strong wire. One end is sharpened and can be easily driven into the drywall with a few twists. It then is locked in place and this heavy-duty helper is ready to display your favorite framed art and photos.