This is an incredibly detailed piece of digital artwork done by Nicolas Kudeljan. He has basically taken the concept of the Starcraft 2 box art (an image of a Terran marine) and created his own image of a Terran medic. It makes an excellent wallpaper 
If you are interested in finding out how this image was made or to see more of Nicolas’s work check out his DeviantArt page here.
Here is another version of the image:
