Some update (thanks @alban):
You can use a Pinboard with a size X/Y bigger than your scene and put your images inside. When you “throw them out”, they will go over the borders and be away from the eyes 
Unfortunately, I wasn’t able to trap drag’n drop events out of the scene, consequence is … I don’t really set the visibility of images to “False”. Images are just out of the scene view but still there and technically visible.
Sample: Community-ThrowToHide-PinBoard.zip (4.9 MB)