Looking for optical illusion playing cards

A few years ago, a friend had a pack of playing cards which had 3D optical illusions on the back of them. That is, all the card backs looked something like this (if you can't see it, there's a horse and rider in this picture). This allowed you to be able to work out what the card was just by looking at the back, since the hidden picture showed the suit and value. That friend doesn't know where they were from, and I can't seem to find them anywhere on the internet. Anyone have any ideas?