Use your own Wallpapers

[cg0]

You can use Kodi File Manager, first you have to delete existing wallpapers, then paste your own wallpapers in the folder the deleted ones were.
You could paste your wallpapers folder inside Kodi's folder if you have issues finding it with Kodi, or use an android file manager to do it -see Android file managers in wiki > Newbies.
The Xenon wallpapers folder for example is in:
/addons/resource.images.skinbackgrounds.xenon/resources/custom/

Replace special://home/Wallpapers with your folder containing your own Wallpapers.