In the case of the X-box skin, Microsoft is well aware of the X-box skin (we showed it to them). That shouldn't be construed as a grant of license but let me put it this way:

If the X-box skin's start menu were pixel per pixel the same (i.e. a direct copy and paste or at the very least merely a modification of it) then that would be an issue. But it's pretty clear from having used it that the author SAW the xbox site and decided to recreate it for his skin. It's not the image, it's a different one.

It still makes unauthorized used of the X-box trademark but if you look on the net, there are zillions of fan sites out there doing the same thing.

One of my favorite sites is called theforce.net
http://www.theforce.net/

If you look through there, they are making heavy use of other material. This falls under fair use. I see the same thing here.