How is Pinterest going to keep going when you know there is "copyrighted" material being posted?
There are sites that tell you "rights determination is your problem" whatever warning they give. I don't know how you track down something from 1923 or 1912. It could be PD or might not. It's an old technology mode of thinking for 21st century reality.
I was trying to find a mystery series I read a couple years ago and after about 40 min I realized how impossible it was since all the search terms were so common. Publishers really like the same stuff but the characters should have different names and different hair color.
Since I don't go to the library anymore, are cozy mysteries still a big deal? They probably are. The rules for writing one of those make you feel like you just got sent to a reform school.