OCLC WorldCat is a union library catalogue with collection information from thousands of libraries.You can use the public search feature to get a sense of the publishing history and location of physical items around the world.
WorldCat Identities helps you discover the extent of publication by and about a creator using an assortment of visualization methods.
The RU Library page for searching other libraries provides links to the library catalogues at all of the universities in Ontario and a few national and internation libraries.
Google other national, university, or research libraries and see what they hold. A cautionary note: old cataloguing rules, manual technologies and financial constraints restricted the amount of cataloguing data prepared for early items. Thus, illustrators of works are not always traced.
Used book databases such as Abebooks.com may be helpful in identifying works featuring contributions including plates or illustrations by particular artists.