Many years ago I did a couple of hundred variations on the mona lisa in photoshop, and stacked them as a gif. As the eyes remained unchanged in each frame, they

Many years ago I did a couple of hundred variations on the mona lisa in photoshop, and stacked them as a gif. As the eyes remained unchanged in each frame, they gave a fixed point you could focus on while the rest of the face strobed chaotically. It was a nice effect.