Hello Lawrence,

the hero image (I think this is the main image you are referring to) is needed to display the portfolio item in the showcase. Short answer it's a custom work involving /sections/hero_section.php

$my_page_id = get_the_ID();

if( $satelite_hero_properties->enabled && ($my_page_id == value_of_the_portfolio_item_id) ){

Haven't tested it but you get the idea. If the portfolio item without the image - do not display the hero section.