Webshots can use the native screen saver on macOS.

To configure this:

1. Create some Playlists in Webshots.
2. Select some Playlists for rotation in the screensaver
3. Go to "System Settings -> Screen Saver"
4. Click one of the photo Screen Savers shown, for instance "Flip-up"
5. Under "Options -> Source" select "Choose Folder"
6. Select "~Documents/Webshots/Webshots ScreenSaver"
7. Note, you can control the start idle time under "Start Screen Saver when inactive" in the Lock Screen Panel of System Settings.

Now you will have Webshots photos when your screen saver starts