May be you don’t like wordpress automatic to store the featured image at your server to save space. so we will use a free plugin named “Nelio External Featured Image” to display the featured image from a custom field

1- install the free plugin located here

https://wordpress.org/plugins/external-featured-image/screenshots/

2- set the campaign to add a custom field named “_nelioefi_url” to contain the featured image src

This applies to amazon products