The following line of code can be used to show the customers rendered product instead of the standard product image. This could be in the cart, or in confimation emails for example.
Simply copy the code below into your email templates, and it will show the customers image:
{% if line_item.properties['id'] %}
<img src="https://app.posterlyapp.io/render_preview.jpg?uuid={{ line_item.properties['id'] | replace: "#", "" }}">
{% endif %}