The October 18, 2016 release of RDA Toolkit includes (among others) the following change to RDA (scope of Illustrative content):

Tables containing only words and/or numerical data are excluded, not considered as
illustrative content. Disregard illustrated title pages, etc., and minor illustrations. 

On the RDA-L listserv, reactions to this change seem mixed. Some appreciate RDA not overstepping (a library might consider a book illustrated when it has an illustrated title page) and others appreciate the guidance this rule has given in the past, anticipating questions about such illustrations from new catalogers.

Illustrative Matter is not a core element in RDA. Even LC PCC-PS only considers it a core element for resources intended for children. So we might consider why we record this element. If someone is looking for a book about musicians, and only wants an illustrated book, is it helpful to include among those results a book that has no illustrations except for a Pelican logo? Or should we only include books with illustrations that supplement the pages’ informative content, or guide the story?