As someone already mentioned, this sounds very much like a one-time pad.  What's interesting, though (to me at least) is that given the new push towards using passphrases instead of passwords, wouldn't it be harder to brute force your way through an image? 

There was some talk, for a while, about using image combinations as a passcode.  There would be an array of 100 unique images and you would simply remember your specific images in order to generate the passcode. 

Ex: Red car, blue berry, green clover. 

While sounding like part of a hearty, healthy breakfast, it also turned out that such a passcode was much easier to remember.  The mnemonic method to remember would be to tell a short story to yourself as you chose your images. 

Ex:  While driving in my brand new red lamboughini, I spun out when I hit a squashed blue berry in the road and landed, upside down in a field of green clover.