Whoever posted those images is going to prison.
I know that the FBI does freckle analysis, and has identified people by photo comparison. If there are identifiable markings in the picture, it is certainly possible to determine if the suspect is the one in the photograph.
It should be assumed that these children are being held by the person posting the images, and every effort from the NSA, FBI, and even the U.S. Military should be used to identify and immediately go to the location.