The default Mate desktop only support single wallpaper.
You need to install HydraPaper.
sudo apt install flatpak
The Flatpak plugin for the Software app makes it possible to install apps without needing the command line.
sudo apt install gnome-software-plugin-flatpak
Add the Flathub repository
flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
flatpak --user install -y flathub org.gabmus.hydrapaper
flatpak run org.gabmus.hydrapaper
NOTE: It should appear under
Menu -> Accessories -> HydraPaper. If it is no there, a restart might be required.
You might see the following message. You can fix this by performing a restart.
Note that the directories
are not in the search path set by the XDG_DATA_DIRS environment variable, so
applications installed by Flatpak may not appear on your desktop until the
session is restarted.
To import photos from directory, click on the folder icon on top-left corner.
To randomly rotate background at interval, refer to HydraPaper Randomly Switch Background at Interval.