Connect your own metafield

Have a File metafield

In Shopify, open Settings → Custom data → Products. When you have no File metafield yet, add a definition with the type File.

Connect it in the app

In the app, open Products, then the Data sources tab. Under “Poster image source metafield”, choose your metafield and click Save.

This applies to the whole shop, and the metafield comes before every other poster image. On a product that already has an artwork area, the same area is applied to the file from the metafield. Check those products, or clear their artwork area.

Set the file on each product

Open a product in the Shopify product editor. In its metafields, pick the file from Content → Files and save the product. Products with an empty metafield keep their other poster image.