The launch of the Windows 8 Consumer Preview version last week introduced the public to a number of new features that had not been seen before in previous Windows releases. One of them is purely for visual pleasure but also very cool; it's the ability to take a desktop wallpaper and have it stretched so that one theme is shown on two monitors.
The official Windows Experience blog offers up more information on these new panoramic themes. These kinds of background can only be used on a PC running Windows 8; they will not work on a Windows 7 PC set up. On the other hand a Windows 7 background can be used on a Windows 8 PC; it simply won't stretch to encompass two monitors. You can check out two Windows 8 panoramic backgrounds, Nightfall and Starlight, at the Windows Downloads web site.