(http://i48.tinypic.com/icppo0.jpg)
Windows 7 only: Freeware utility Windows 7 Folder Background Changer adds a background image to Windows Explorer, and even allows you to customize each folder with a separate picture.
Once you've downloaded and extracted the no-installation-required application, you'll probably find that you need to right-click and choose "Open as Administrator" the first time you launch the application, but otherwise it's fairly straightforward to use—just choose a folder to customize, pick the background image and the other settings, and then close and re-open the Windows Explorer window to see the changes.
It's not really going to help you get more work done, but if staring at a white background is getting old, it might be nice to have a better looking workspace, at least. Windows 7 Folder Background Changer is a free download, works on Windows 7 only.
Windows 7 Folder Background Changer
(http://i48.tinypic.com/2zgyzh5.jpg) (http://www.thewindowsclub.com/windows-7-folder-background-changer-released)