A handy new list of Tolkien’s Published Art, which is a newly-revised update of the art section to be found in J.R.R. Tolkien Companion and Guide: Reader’s Guide (2017 edition). It’s kindly been placed online for free by the authors, in PDF.
Incidentally, I see that I previously wrongly called the Companion and Guide a third edition, in a previous and hasty “oh, gosh look!” blog post. It’s actually the second edition, and my error here has been corrected.