One of the nice things about KDE is that it has some neat functions built in, and one of the best is the ability to set a different image on each desktop and if you want, each activity.
Among the options is a desktop slideshow. Not that is a nice touch, but the KDE developers hard coded the slideshow to show images form any selected folder only in RANDOM order. And not all of us want a random slideshow.
Fortunately there is a way to get a sequential slideshow happening and the way to get around this is shown at:
This method is ONLY needed if you DO NOT want random images.
KDE Default Desktop Settings and choose 'Slideshow' works perfectly for random images. No need to do all this stuff.
I take photos and often want to show a sequence of zoom shots, so I use the method below.
So the basics are Install variety:
sudo add-apt-repository ppa:peterlevi/ppa
sudo apt-get update
sudo apt-get install variety variety-slideshow
Then run variety and set your preferences. I just added the folders I want to use and turned off a lot of background downloads I don't want. And I set the timer on the slideshow.
I made sure I have it set to start variety when the computer starts.
Once that is done, open your 'Default Desktop Settings' and choose:
Wallpaper > Image
Then choose Add Folder, and browse to:
Pictures > variety-wallpaper
click on the image in that folder. It will be called something like:
wallpaper-kde.jpg but will have a number in it.
Click OPEN, then click OK
It 'should' be working now.
After that, to change the images shown, open variety and change the folder you are using there.
You can still use Default Desktop Settings to go back to a normal single image at any time. To get back to your slideshow just open the wallpaper-kde-xxx.jpg again using the steps above.
Of course, this will leave variety running all the time even when you are not actually 'showing' the slideshow.
I'll have to look at how variety can be switched on and off at will and add that here.
Two things I discovered.
When I restart my computer KDE will default to a generic single image wallpaper. I must restart variety and go through the image selection steps for each session.
Variety can be started and stopped using terminal commands:
Entered on its own will start it - then I select the image as described above.
Will stop it, and should leave the last used image, but might return to a default wallpaper image.