Apple Tweaking More Icons, Upgrading to HiDPI Sizes in OS X 10.7.4 – Mac Rumors

For some time now, OS X icons have come in various sizes up to 512 x 512 pixels. Over the last couple of 10.7 Lion updates, Apple has increased the sizes of some icons to 1024 x 1024 pixels—notably TextEdit and Automator—presumably in preparation for what could be Retina upgrades for Mac displays.