2015 is a bad year for viewing private Facebook pictures. Not only have Facebook really come down hard on people trying to hack other user's accounts (they dish out instant bans and even legal proceedings), Facebook has also started paying out to any hackers that discover loop holes or gaps in the privacy and security of the social network.
These sums are usually quite large, which means that every a new hack is discovered, it is usually reported and closed down very quickly.
For example, I saw a post about a new Facebook hack in 2015 on Reddit, and I tried it out and it worked.
3 days later, I tried the same method again, and it threw up a sever error, suggesting Facebook had patched the bug.
As well as upping their security, Facebook have been spending a lot of money on moderating and cleaning up the platform.
I now several people who have been suspended for breaching the terms of service, and more than a dozen friends of mine were asked to update their names because Facebook moderators suspected them of using fake names, and requested a copy of their passport in order to keep their account active!
What does this mean if you're trying to view private pictures in 2015? The suggestion would be to forget about Facebook, and try to find a website or app that is newer, has less resources, and possibly more vulnerabilities...