For t-shirt design, it is a must. Customers printing on the back of the t-shirt have the impression that the output in not correct.
We can see both in the preview but not in the cart.
Displaying both or multiple thumbnails of the view can decrease the performance when adding the product to the cart, so we do not think its a feature that is relevant for the majority of FPD customers. If you still need this feature, you can contact our customization team:
This would be a great feature, if the cart and customer order-email thumbnails could show front and back views of the product.