Currently this is only available in our Shopify app but it is a feature that we have in the pipeline for the Manual order form and API. 

Our App generates lay-flat product mockups, which you are free to use as you see fit (including outside of Shopify).

If you’d prefer to use a different style, you’ll need to source an alternative mock-up generator, or generate them yourself.

Quite a few of our customers use Creative Market to generate mock-ups in photoshop or indesign. 

If you’re looking for mock-ups featuring real people, PlaceIt has a great selection of photography and has recently started offering video.