It is me again with my wicked plans!
So consider this: You have a lot of personal photos and you would like for your new UM install to start a carousel all of them in your background.
Now, if you're anything like me, you will have issues right off the bat (Ref.: /usr/bin/variety stopped working due to new clock/time format? )
So let's consider only native UM tools.
Here's what I would do: single right click on background -> change desktop background then I would be facing several thumbs into the "background" tab. All of that is normal as of yet.
Now, to get the hostilities started: I have made myself a ~/Images/backgrounds/ in order to dump all of my favorite jpegs over time and (ideally) simply refer to this folder as my background references.
Problem #1: in order for my backgrounds to be 100% custom, I first need to manually select and delete e-v-e-r-y already existing entry. I can do that but I surely won't be happy when I'll have to setup a new system from scratch and have to redo all of that mundate/useless work. Of course, I cannot select multiple entries and click once on "remove", I need to do them all one by one.
Problem #2: Now that I finally gotten rid of everything (minus that 1st/default entry that I cannot remove), I can now add my content. So "Add" is the first thing I hit and planning to point on ~/Images/backgrounds and select all of my pictures and bingo they are in! But look at that: no "randomize option" available. Meaning that I will have to manually change my pictures? Hmmmmmm....
Problem #3: Only external binary that I know which would help (/usr/bin/variety) segfaults because of clock settings.
Solution #1: IF/WHEN we ever get a more complete "Personal" section/wizard could we make sure that user could have his/her custom backgrounds automatically imported during session configuration wizard?
Solution #2/Problem #3: I know of the screensaver "carousel" for picture rotation. But not only is this not what I want, it also doesn't seem to be working "out of the box" post-installation. Even after I have deployed "xscreensaver-data-extra" and "xscreens aver-gl-extra". Looking under "Screensaver Preferences", selecting "Carousel" and then "Settings" does not hint me at anything. Of course, selecting "Carousel" from the default "Screensaver" entry fails to display me configuration options.
After briefly googling that issue out I figured out once again that my esoteric requests would best be channelled via this, oh, so great Community.
So that's it folks: my current state of things in terms of UM latest's screensavers.
Guess nobody has those problems and needs or that they find it too mundane to bother posting it here?
Rest assure that I will be back sooner with another unique and... real life changing issue very soon 
Thanks for reading yet another one of my funky post and not shooting yourself in the process.
DLS