I do not have the wallpaper option in settings

I am doing work in a school who has locked down their idpads. somehow a student changed the background/wallpaper and I am being asked to change it. when i go into settings, I do not see the option for "wallpaper". Does anyone know of a back door to change it or how to reset the device without loosing any of the apps already downloaded? They use the MDM Profile platform.

Thanks,

Phil