Lower back butterfly tattoos are usually larger, more stylized butterfly images that stretch across the lower back, one of the most popular places to get a tattoo nowadays (but also known as a tramp stamp).
Actually, butterfly tattoos lend themselves very well to this location. The butterfly image is very symmetrical, so the middle can easily be lined up with the spine, the wings extending on either side. This makes the butterfly wings longer and more stretched out than they would be in nature, but the image can be very attractive.