Rejected my work "Postcard Vertical. Top View. Mock-Up v1"

Rejected my work.
I want to know your comments.

hi I think that u should ask @DesignSomething he is the most likely to give u a clue for such a type of item

The Mock-up is too simple. Add more isolated elements (like 3D basic shapes) that helps customers to create unique scenes.

Many thanks!
Totally agree with you