Would you believe if I say this harmless looking image is actually a .zip file (less than 2 Mb) containing 31 .rar files each containing an html file which has one of the works of William Shakespeare? Well it is exactly what it is. This sort of hiding encoded data in images is called Steganography and it is a widely researched subject in its own right. This sort of technique was used during war times to send or hide secret information in plain sight.
But what makes this special is that this image was created and tweeted by a UK based researcher named David Buchanan, effectively using Twitter as a file sharing service. Aparently Twitter is aware of this and doesn't consider this as a security vulnerability.
You can see the original Tweet here