Not true on images can be used for educational purpose. Etiquette is
to ask for permission on anything. True, some things you can not get
permission. While I can not quote exact information, I do remember
recently that ancestors of Famous Artist are beginning to protect
images of the artwork. I do know that portraits, such as those of
MLK, are protected. If the family gives me permission to use, it does
not mean any teacher can use the image. I was given permission. I
really adhere to copyright issues with my students. Unless they get
permission, it is not used. As far as historical artwork, I show from
the web page but do not download into a presentation unless the
copyright information on the site states I may do so or I ask the
webmaster. Images from United Streaming are granted permission for
Educational use.
I am still have a lot to learn but I do not use the fact that I am a
teacher and it is for classroom use as a reason to just take anything.