Photo Viewer Background Changer is my latest work. It allows you to change the background color of built-in Windows Photo Viewer and Windows Live Gallery. See this:
Spoiler
Photo Viewer Background Changer is portable application and doesn't require to be installed. It supports the following products:
- Windows Photo Viewer in Windows 7
- Windows Photo Viewer in Windows 8
- Windows Live Gallery in Windows XP
- Windows Live Gallery in Windows Vista
- Windows Live Gallery in Windows 7
- Windows Live Gallery in Windows 8
Note: .NET 3.5 is required for Windows XP and Vista.
Download link