I hope this is the right place to locate this thread. If it isn't I'm really sorry, but I was wondering if anyone knew what the wallpaper with the mountains/lake that is on the MBP on the aperture website is.
That looks like it is a custom professional photo from Apple's ad department, meaning that they paid for it. Try searching "mountain lake" at either of the sites below.
A lot of the desktops, especially landscapes, in March Desktops come from these sites. That may have been a better place for this qurstion but they would probably give the same answer.