One of the most useful tools for image-related scholarly research is Artstor. However, be mindful of copyright restrictions - you can use them in your homework, presentations, password-protected education websites (Canvas), and personal use (inspiration) but you must research copyright permissions for each image for public use/publications.
Sometimes your art object will not be available from a reliable electronic source. In these cases, your next best option is going to be finding the object in a book.
In the library catalog search for your artists' name, then try to find items that are exhibition catalogs, retrospectives, or catalog raisonnes.