This seems like exactly what I was looking for! However a small suggestion: Can you add a field for image upload aswell?
What I'm trying to do is to create custom items, allowing the customers to upload their pictures aswell on the design. For the design, I can add that as products and make it selectable, but for the photo's, I would typically need to ask them to email the picture or find another way. Having this integreated would be really useful! Great contribution you got here!