Lots of beautiful cards in this thread. But the most aesthetically pleasing card is almost surely a common - there are just so many more common players than there are stars, the odds are way against it being a star player.
That said, I don't collect commons, so my nomination is also a star player.
Lots of the good ones have already made an appearance, but I think 52 Mize hasn't shown up. One of my favorite cards of all time.