When you think about it, the number of distinguishable photographs is countable. The human vision system has a limited resolution. Nowadays, five megapixels is hardly distinguishable from a four megapixel image. So that means that each picture is about 5 million pixels for a 5 megapixel picture. Human vision is pretty sensitive to color, but it's limited at about 24-bits, or 16,777,216 colors. So there are 5 million * 16.77 million = 8.285x10^13 distinguishable pictures.
That's a lot of pictures, and it's hard to comprehend how big that number is. The vast majority of these pictures would be noisy-like. But when you think about it, every frame that you've ever seen on your TV, every digital photo you've ever seen on flickr, every image you've seen on your monitor have been a subset of these 8.285x10^13 pictures. And yet, you have not seen the vast majority of these pictures. Some of these are pictures of people you know, people you don't know, places that you've never seen, deserts, planets, stars, aliens on their home planets in their vacations, even. Pictures of the imaginary, of dreams, of the impossible.