In case the doubts still exist, with this tutorial I hope to dispel them a little ... KDE It is an environment that undoubtedly allows the user to configure their computer in a much more varied way than any other environment, here I will teach you everything related to wallpaper.
Actually, all these options can be found in the configuration panel, while in Gnome (for example) to achieve much of this it is necessary to install new applications, many times that do not achieve everything you want.
But hey, enough since then a flamewar is set up on KDE users explaining with tests and objective answers, about KDE allowing more than Gnome, and Gnome users trying to debate with the only argument that this environment (Gnome) consumes less hardware than KDE (which is true).
Basic options:
The intuitive, the basic thing to configure the desktop is to click on it and we access Desktop Preferences, there we will see the most immediate options we have. As we will see in the following image, we have two tabs, one for the immediate options for that desktop, and the other related to mouse gestures:
In this tab, we can define how we want our wallpaper and what it will be, as well as specify that we do not want a fixed or static wallpaper but that we prefer a presentation or gallery, this is achieved by selecting in «Wallpaper»The option of«Presentation«:
Customizing each desktop:
We have just published a simple tutorial, through which we explain how to use a different wallpaper on each desktop: https://blog.desdelinux.net/wallpapers-diferentes-escritorios-de-kde/
Well, following that tutorial we can also place different widgets or plasmoids on each desktop. In other words, if we configure our desktop to have a different wallpaper on each desktop of ours, the widgets, plasmoids or gadgets that we have may also be different on each desktop.
Conclusion:
Wallpapers in KDE can be either fixed, or if we wish they can be a gallery or a presentation, and this is achieved without the need to install external applications or anything like that. In addition, we can have different wallpapers on each desktop we have, allowing us greater customization and why not? … greater beauty on our computer 
Greetings 