Due to "customer" demand I've quickly put together a gui and crontab python libs for setting auto changing wallpapers. See screenshot attached for demo.
You need to install 3 debs, 2 python libs and one app. It'll put a menu item in your system > preferences folder for you to configure it.
This is new, so report bugs here: https://code.launchpad.net/gnome-wallchanger
Download via PPA here: https://launchpad.net/~doctormo/+archive