Not really possible in Photos. Albums and pics are private by default, meaning the public can't access them unless you give the URL...BUT the pics will still show in your timeline. Maybe you could throw private pics in Google Drive and disable the option to view them in Photos?
There is nothing private in Google, these animals will get to your shit in no time.
I am trying to fend these delusional fools off invading my privacy, driving white and blue ford cars around looking like a fool. I wanted to ram one today as I was leaving for work.