While perusing High Snobiety, I came upon a post about a release of Mac OS X Sneaker Icons. They just released a pack of 13 shoes with more coming soon. The first set are all Nike and they're totes free.
Orange Claw Customs was started by two Sneaker/Mac lovers in Melbourne, Australia. The Boy's mission is to deliver super high quality system icons of cult sneakers from all the biggest names in footwear. The icons are for use on Mac OS X, and soon Windows XP. The two founders created the site to coincide with their belief that sneakerheads should be able to cover every aspect of their computer with sneakerama. The custom section of the site also allows for requests for specific models and colourways.