An Afterimage Face
This is an afterimage effect, which is also shown by the Amazing Dots. An afterimage is a visual impression that remains in the retina after the initial stimulus is removed; however the afterimage is the opposite colour to the original. So if you stare at a black square for a long time and then look away, the after image will be a white square.
This image is effectively a 'negative' image of a face; after you have looked at it for a while, the afterimage is the normal face.