Facebook last increased photo sizes from 604 pixels to 720 pixels back in March 2010. Despite being a 20% increase, 720 pixels photos are not just that big here in 2010.
Apparently, Facebook agrees.
Facebook is now increasing sizes even more, from the 720 pixels to 2048 pixels. Much better – good job, Facebook!
They’re also changing the way photos are being displayed as you’ll see the big photo in the middle of the page and with black around it. 2048 pixels should even be enough for you to be able to print the photos in a reasonable size.