NeoDownloader - As you know, there is a lot of websites with a lot of pictures, music and movies.
John's Background Switcher - Switch backgrounds to trending imgur, reddit, tumblr threads
Vov Picture Downloader - Download pictures from websites.
Unsplash Wallpaper - Gorgeous wallpapers on your Mac
Persepolis Download Manager - Persepolis Download Manager is a GUI for aria2.
Wallcat - Enjoy a new, beautiful wallpaper, every day.