This may or may not be, but I do think it's an iTunes 7.5 feature. I'm thinking they must have included a QuickLook plugin with iTunes 7.5 so that QuickLook can view album art embedded in a file. It definitely didn't work for me before 7.5. After updating, even a couple files that were already on my Desktop are showing artwork icons.Think it only works when artwork is embedded into the file. Not all the Mp3's have the artwork embedded into them.
That's odd because I only got the feature with iTunes 7.5? It seem's like everyones Leopard has a mind of it's own, in terms of all the different results people are getting!I've noticed the album art showing as the file icon since the first day installing and using Leopard. Was commenting to my sis it was a nice touch.
The feature came with Leopard, not merely with iTunes 7.5.