Art Storefronts offers its Print Studios, Artists and Galleries the ability to use the custom framing feature in their Uploads and Art Print Stores. The only restriction is for those Artists who are using Automated Fulfillment. If you are using a Fulfillment Vendor you won't be able to create custom frames.
When you are setting up your website you will find (unless you are using Automated Fulfillment) that there will be a tab in your Art Print Store or Upload Store labeled Frames. When you click on it, you'll be able to create your own custom frames and provide previews of them.
If you would like to know more about the framing tool or setting it up, please see our article: How To: Create A Custom Frame
If you are a Print Studio, Gallery or Self-Fulfilling Artist and you want to add the cropping tool to your site, please e-mail cs@artstorefronts.com.