Including the title and author of a work helps readers to easily find out more about that work. When possible, including a link directly to the page of the source makes content richer and more useful, keeps the author of the work happy, and demonstrates competence as a communicator.
How To Credit
Include a meaningfully described link to the source. While checking the link, find the proper title of the work, and the author's name. Unless specified otherwise, credit work you reference with an attribution like this:
“Artwork Title by Artist Name”
If you have access to the html of your page, the easiest way to create a relationship between the work and the attribution is to create a figure element, and use a figcaption element–child for the attribution. A cite element should be used for the title.
For extra credit, use semantic markup. Here is a list of visual artwork properties from schema.org.