I changed the wallpaper and it didnt change back.
https://support.microsoft.com/en-au/help/4026102/windows-10-about-sync-settingsTo stop syncing your settings and remove them from the cloud, turn off synced settings on all the devices connected to your Microsoft account, and then go to the Devices page, select More actions for the device you want to manage, and then select Remove cloud backup of personal settings.