Only works for new photos posted after you turn on this Applet and will skip any GIF posts. Be sure to create and choose the Dropbox/IFTTT/TumblrScreensaver folder in your screensaver setup.
OSX: http://apple.co/2p7XmxK
Windows: http://bit.ly/2qE6fPt
If
New photo post
This Trigger fires every time you create a new photo post on your public Tumblr blog.