Regarding Profiles you do not have to post pictures of yourself, and you do not have to post your real name if you don't want to. Most user names on here are just that - user names. Profile pictures and avatars can be anything other than a picture of yourself.
You can also set permissions for who can view your profile or not. Go to Settings at the top of the page, then look under My Settings and click on Profile Privacy. There, you can choose who can and cannot view your profile, avatars, etc.