I logged out of my mac and I noticed my display picture was gone. I never deleted it and the user & groups setting in system preferences is locked. does anyone know why this could have happened? it's also the for the administrator account?
Go to system preferences, click on users and groups, if the account you are currently using is monitored, (parental controlled), the person that is the admin can change and lock it. If you are the admin you can change your profile picture by clicking on the profile picture, when you hover over it, it should say "edit" on the bottom of it. Click on that and you'll be able to change it. Hope this helps... if not... please reply to this message.