To install, simple download this script on a desired location and configure a crontab job to execute it every time you want.
If your wallpaper are in a different path, modify accordinly on the script
Same apply for /usr/bin/gsettings
# change wallpaper every 15min. Change {usr} or the whole location to match yours!!!
*/15 * * * * python3 /home/{usr}/wallpaper-randomizer/wall-randomizer.py