在模板中尝试此代码。

$query = new WP_Query( array( \'post_type\' => \'custom-post\', \'posts_per_page\' => -1 ) );
if( $query->have_posts() ){
    while($query->have_posts()){
        $query->the_post();
        $image_query = new WP_Query( array( \'post_type\' => \'attachment\', \'post_status\' => \'inherit\', \'post_mime_type\' => \'image\', \'posts_per_page\' => -1, \'post_parent\' => get_the_ID() ) );
        while( $image_query->have_posts() ) {
            $image_query->the_post();
            echo wp_get_attachment_image( get_the_ID() );
        }
    }
}