Most of my site designs use oversized backgrounds. As a long-time owner of 30" and 27" monitors, I always appreciated other designers who utilized the 2560 pixels these monitors had to offer; this shot of Chicago for the background of motionbusinessservices.com was a phenomenal example of why I love these images.
At a normal browser width, the entire bean is encapsulated in the browser. For those with larger monitors, they get the full view of this amazing cityscape.
The design here is simple: it's a consulting business website built on a CMS (Drupal) with very little styling -- that was the concept; simple, clean and unobtrusive. Each page uses another oversized image, yet the entire site feels cohesive.