Wallpaper Downloader makes it easy to customise your desktop wallpaper by automatically downloading and using the latest Bing images.
Launch the program and it will download the latest 10 images from Bing.com, then automatically change your wallpaper from one to the next every 15 minutes.
Not happy with that? You can change the frequency to anything from 12 hours (would work well) to 10 seconds (probably wouldn't), as well as customising how the wallpaper is displayed (it can be tiled, centred on your screen or resized to fit).
And if you don't like a particular image then you can always click Previous or Next on the program console, and it'll cycle to something else.
While this works well enough, the program does have a couple of issues which may put some people off.
The first irritation is it wants to display a "What's New" box every day, presumably because this includes web ads which the authors hope you'll click occasionally. This can be disabled from the Settings dialog, though.
The other issue is that you must create an "account" before you can use the program, giving them your email address and a password. Which is a little annoying as we see no real reason why you should have to do this, although the authors do at least promise not to share your details with others.