MakuluLinux uses Variety Wallpaper changer. It takes control of all your wallpapers and desktop quotes, it will change your wallpaper and quote after every reboot and also after every 2 hours. You can edit the content and frequency of how it manages your wallpapers in the variety settings. Or, if you prefer the old fashioned manual method, then disable variety. Variety can be found in the bottom panel next to the clock, or in the main menu under accessories.