LXDE screensaver configuration (Trisquel mini)

In the screensaver configuration of Trisquel mini, there are a large number of options but, for the big majority, when selecting an option, it says it is not installed. Does anyone know how to install them?

Besides, is there any option that is a slideshow of images in a folder, much like a similar option that exists in Mate?

I know the command "feh -F /path/to/images" to make such a slideshow, if there would be a way to configure the screensaver to run a command, that could do the thing.

By the way, if anyone knows a slideshow command (I really prefer something in command line) that does some fancy transition effects between pictures (feh has no transition at all), I am interested.