We are launching a range of decorative abstract art, printed on canvas. As a showcase and e-commerce gateway, we based our web site on OpenCart (PHP Open Source), and found it exceptionally good for this purpose.
Some of the artwork is traditional media, but a lot is generated by software, including my bespoke applications.
OpenCart was perfect for the showcase and handling purchases. It is an open-source PHP CMS. It uses a straightforward template system, easy to understand. I have found several cases where I wanted to make small customisations, and it has always been easy to locate the right spot to adjust. The "out of the box" W3C compliance is good, so helping to ensure consistent display across browsers.
There are modules for various payment and shipping rules, including discounts based on value of order. I am very impressed and will be happy to create an OpenCart site for your project.