Where is my Skype profile picture stored on OS X?

I've just tried this, and the answer was unexpected...

When I created the image it was stored in the following folder (before Mountain Lion):

~/Library/Images/IChat Recent Pictures

Please note that as per skh's answer, since Mountain Lion (and still valid for macOS Sierra) the images are now stored in the following folder:

~/Library/Containers/com.apple.ImageKit.RecentPictureService/Data/Library/Images/Recent\ Pictures/

Took me a while to find this, but here's the profile picture directory in Mountain Lion:

~/Library/Containers/com.apple.ImageKit.RecentPictureService/Data/Library/Images/Recent\ Pictures/