Source: An Example of Photography on the Retina Display - Duncan Davidson
Stashed in: iPad!, Images!
tl;dr; Use Progressive JPEGs (and party like it's 1994)
That. Is. Amazingly. Crisp.
Review of FiftyThree's Pencil Stylus for iPad
The most popular tweet of all time:
Maybe the Most Badass Photo Ever Taken - August 1960
When Michael Collins took this picture he was the only human, living, dead or unborn, not contained in the frame of it.