The majority of the background images weren't taken by the office. Those that were sourced by a 3rd party were taken by 'Reading Tom.' They were all sourced from the album linked directly after this.
https://www.flickr.com/photos/16801915@N06/albums/72157711422425273
Below are the differences made between the images.
Original image
Used Version of Image
Original image
Used Version of Image
Original image
Used Version of Image
Original image
Used Version of Image