This image is from the collection of German filmmaker Werner Nekes.
The Hayward Gallery showcased the Werner Nekes Collection in their exhibition Eyes, Lies and Illusions. A companion to the image above is the image on the poster below (which you can click to enlarge.)
The original images
The above "skull / man" image is also on the cover of the book Eyes, Lies And Illusions: The Art Of Deception by Laurent Mannoni, Werner Nekes and Marina Warner, Amazon>>
– Optical trickery from the exhibition Eyes, Lies & Illusions>>
– Werner Nekes>>