if( ! function_exists( 'kappa_featured_posts_thumbnail_size' ) ){
    /**
     * Hooking into the featured posts widget thumbnail size.
     * @param unknown_type $size
     */
    function kappa_featured_posts_thumbnail_size( $size ){
        return 'large';
    }
    add_filter( 'marstheme_featured_posts/thumbnail_size' , 'kappa_featured_posts_thumbnail_size', 20, 1 );
}