В шаблоне /themes/default-bootstrap/category.tpl изменить
<!-- Category image -->
<div class="content_scene_cat_bg"{if $category->id_image} style="background:url({$link->getCatImageLink($category->link_rewrite, $category->id_image, 'category_default')|escape:'html':'UTF-8'}) right center no-repeat; background-size:cover; min-height:{$categorySize.height}px;"{/if}>
на
<!-- Category image -->
<div>