Dude, that's the most annoying wallpaper I've ever seen. There's two colors, and their very vivid, and that grass looks like the plastic stuff anyway. I hate it! Jeez. there's no movement, nothing interesting, nothing exciting, no artistic value whatsoever, there's just no reason to look at it. And that blur of the sky is totally unnatural.
Duck's wallpaper is awesome though. It's a picture of the USMC Memorial--US Marines raising the Flag on Mount Suribachi during the Battle of Iwo Jima. The subject of the image is very interseting. The picture raises emotion from deep within your mid, makes you think of the event, and gives you that "feeling". The color of the picture is meant to help raise these emotions. As you can see, Duck's picture is better in every way. Matt's picture sucks and I hate it.