Art Storefronts has implemented a feature that shows potential customers products related to the product they are currently looking at. This is a common feature across multiple platforms. Take for instance, Amazon. When you go through the purchase process of Amazon, you will see a suggested or related products section toward the bottom of the page. Art Storefronts implemented the same type of feature to all Art Storefronts websites.
These Related Products are chosen based on the name of the image first. This means if the name of the image is related in any way to the image the customer is looking at, it will appear in the Related Products list.
In addition, you can also work to edit these by implementing Product Keywords. These will allow you to have a bit more control over the list of Related Products.