If you were believing that simply by moving your photos away from your Facebook timeline using the "Hide from timeline" feature really made them unreachable to be seen, we're sorry to disappoint you, but you were totally wrong. This new app called PictureMate (its original name was PictureBook but Google took it down because of its name making it looks like is pretending of being a Facebook extension) pretends to "View hidden photos of anyone on Facebook" regardless if the target is in your friend list or not.
PictureMate is a free Google Chrome extension that gives you abilities to view any picture of anyone on Facebook who's privacy is set to public. Remember that no application or neither any extension can change your Facebook privacy, what this app does is simple, it surfs over your uploaded and shared pictures of yours along with other pictures where you are tagged and who's privacy is set to public. Even if you removed these photos of yours from timeline or the photos where you were tagged you didn't really changed the privacy of the post. That's the maximum this app can do to find your photos.
If you want to make sure that none views your hidden photos you must change their privacy and about the tagged photos if you have no power about switching the post's privacy then you will have to remove the tag because there will surely be and many other similar apps to PitcureMate in the near future.
PictureMate is created by a guy from Singapore who's name is not known for me but his Twitter account is @Nubela and he is also the founder of Javelin Browser. If you want to try to view hidden photos of anyone on Facebook try to install PictureMate extension (remember that will will need Google Chrome browser).