When you upload your photo you have the choice on who gets to view your picture. You may choose "everyone", this way it is visible in the site gallery for all to see. You may choose "friends", this way it appears only in your profile page gallery and only your friends may see it. Or you may choose for "nobody" to view your photo and this way it is only viewable to you and does not appear in the site gallery and it is not viewable by anyone, even your friends.
