Oh, hi guise! I found a loophole on how to do this. I'm sure Facebook will shortly catch on, so I suggest trying this soon before they do.
EDIT: More specific instructions
Step 1: go to the private profile with pics you want to view and press "report/block"
Step 2: ONLY select "Inappropriate profile photo", continue. Only select "Nudity or pornography", continue. Only select "Report to facebook", continue. Only select "Help us take action by selecting additional photos to include with your report", continue.
PROFIT: It'll let you see a bunch of their pictures (in thumbnail size, but still viewable). SUCCESS!
EDIT 2: USE SPARINGLY!!!!!! as to avoid any repercussions Facebook might implement on you.