Try a One Stop Search - limited to the BU Library Catalogue. Perform your search, and then look to the left side of the page. Find the Tweak My Results options. You are looking for those identified as Audio Visual.
Some Image searching is available on the BU Library Catalogue. Perform your search, and then look in the Tweak My Results section (to the left of your results). If the limiter Images is available, it will be listed in the Resource Type section. For example, try these sample searches:
"national gallery of canada"
Once you have a result set, look for and select Images from the left side - Tweak My Results. The results will then be records for online images that match your search terms.
Note that this search will NOT return all images for any artist. For example, to find examples/photos of works by Wanda Koop, you might perform the search Wanda Koop. You could then examine the Images options in your results, as well as identify other books, articles, and so on in the results list for this artist. Also, note that Images will not be returned for all artists or art-related searches. However, other results (books and journal articles, for example) may contain images of an artist's works.
The Fine Arts Online section of this Library Guide offers a list of suggestions of online sites for topics in fine arts - including museum sites, art organizations, lists of artists in specific categories, and options for art history information and Reference.