Digital Blasphemy ( at http://digitalblasphemy.com/ ) is a great desktop wallpaper site.
There are always about 50 free wallpapers available. This WordPress widget allows you to show thumbnails of the free wallpapers.
You can choose to show a single random thumbnail from the pool, or the latest freebie.
Some basic CSS is included. If you’d like to turn it off, drop this code into your theme functions.php file or a plugin of your choosing.
function db_styles() {
return false;
}
add_filter( 'digitalblasphemy-styles', 'db_styles' );