Imho, all rules for any game should be stated clearly at the initiation of the game thread. Unfortunately, most of the time on any message board, since most members aren't professional game starters, this isn't the case. For the longest time in this game we've acted under the assumption that in order to successfully guess a submission's solution we can google actors, scenery, anything which might help us, but not the image itself. It's possible to use a copy of the image to find out which movie it's from. This habit has been considered "cheating".
As soon as we allow the above habit this game is no longer a game but a silly pretense, less useful than tossing a ball back and forth.