cam2pc has the ability to set any image as your desktop wallpaper. This option is available in the Image Browser and in the full-screen viewer.
One other interesting option is the possibility to have cam2pc regularly update your desktop wallpaper with an image randomly picked in a folder.
You can enable this in the Wallpaper tab of the Options dialog. Set the time between two updates (in hour/minute/second), select a folder and enable the recursive option if you want cam2pc to take all the sub-folders into account.
Please note that this option requires the cam2pc tray icon to run permanently on your PC.