AppData is system solder and it is hidden. You either go to folder options and check the option to view hidden folders or just open My Computer and paste the link (C:\Users\Username\AppData\Roaming\Microsoft\Windows\AccountPictures) in the address bar. Be sure to replace Username with your user...
Go to C:\Users\Username\AppData\Roaming\Microsoft\Windows\AccountPictures and delete all pictures that you want to remove from there.
http://www.eightforums.com/tutorials/34801-account-picture-delete-recent-pictures-windows-8-a.html
