Gnome Slideshow Background XML creator lets you create an xml file from pictures in a folder that create links to all your pictures. Just add the xml file to background tab in appearance window and you are done.
The application is .jar file so you will need Java or OpenJDK installed.
- Right click the file, go to properties and set it as executable in permissions tab.
- Right click and select open with Java or OpenJDK.
- Click on browse to set your folder and select create XML.
- Go to System>Preferences>Appearance and to the background tab.
- Click Add and select 'all files' in the bottom right corner.
- Select the xml file you created.
Edit: The developer have now included the options to set timing and duration in GUI itself. So no need to edit xml.
Download from here
Thanks to kenster421@gnome-look