You have to echo out the call to the image
<div class="page-banner" style="background-image: url(<?php echo Categories_Multiple_Images::get_image( $cat_id, '1', 'full', false ); ?>); background-size: cover; background-position: center top;"></div>
I used get_queried_object()->term_id on the archive page to get the category id. Hope that helps!
