Sometimes it's useful to not include product images in the documents, for example to save space on orders with lots of products.
You can remove product images by doing the following:
Login to Order Printer Templates (Shopify admin -> Apps)
Click the "Customize template" button on your design
In the editor, go into the "Options and formats" section
Adjust the "Product images" dropdown to "Do not display"
You'll see that the preview updates, and the product images are no longer shown.