I have not used this program for a while due to using another wallpaper changer. Today, Jan 6, 2019, I started it by accident, and discovered something new. The art that I had seen before was not shown; instead, a photo was shown, so using the System Tray icon, right-click options for the app, and choosing “Show Artpip.” There is now a statement at the bottom of the program’s display that states “Unfortunately, Artpip has had to change to photography-only.” I checked the website for Artpip and it is now free (no longer is being sold as a product).
The art pictures were probably copyrighted, which forced them to no longer distribute the images.