As a teacher, I'd like to jump in on this. "Educational purpose" is broadly-defined, and, in my experience, never enforced. I teach a unit on mental illness every year to my juniors and follow up with the movie "A Beautiful Mind". No one has ever asked me to correlate it with my curriculum in over ten years of teaching. Similarly, my neighboring teacher plays "Frozen" frequently...and is also never questioned.
I suppose all it would take is a disgruntled parent to call someone, but I have not heard of it happening.
In one of the links I provided, it was noted accurately that there have been only a handful of cases in 200 years where a school/teacher has been sued for infringement over the unauthorized showing of a film in the classroom - although there have been cases where the school has had to pay after-the-fact for a discovered unauthorized use (generally requiring the school/teacher to pay the licensing fee that was required prior to showing the film).
But, as also noted in one of the links I provided, an educator needs to be careful to obey the law. Some of the laws that need to be followed by the educator are copyright laws. Teachers should note well the "warning" about copyright infringement that is shown at the start of a film. If the film has been licensed for use in an educational setting, no problem. If the film has not been licensed for use in an educational setting, the teacher should know what is considered fair use and what is not a fair use of copyrighted material.
In other words, just because everyone is doing it and not getting caught does not make what is being done any less illegal. Since this is a legal forum, I think the law needs to be cited and respected as the law.
To LdiJ: If alternatives to painting a mural had been requested by the poster (or even if alternatives hadn't been requested), I could have more easily accepted what you wrote. But what you wrote went beyond simple alternatives to painting. You suggested the poster create on the library walls what could be considered a derivative work. Creating a derivative work would not be legal without permission granted from the copyright holder, just as using a copyrighted film without authorization from the copyright holder would not be legal without permission granted from the copyright holder. Permission generally comes in the form of a license.
This is not even addressing your other statements that needed correcting so that the poster would not violate the law based on an incorrect understanding of copyright laws (and an incorrect understanding of what is a public place, what is a derivative work, what is an unlicensed work versus a licensed work, etc).
It also does not address your failure to provide a source for your information until you were prompted by justalayman and his post (based on research by justalayman). Even now you have not provided an actual source. You are stating these catalogs exist but, with nothing more than your statement, it is hard to determine what sort of licensing comes with the purchase of items from the catalogs. If these purchases come with licensed rights, what sort of rights are being granted and by whom? What is the scope of the rights that are granted? Having a source would help.
I am afraid the obtuseness is yours, LdiJ. Have you read ANY of the information that was provided in the links? It seems doubtful.