This is my setup for the Custom Walker Menu we discussed at the AWP meetup. I've included the shortcode setup as well that allows the user to past a simple shortcode that will spit these custom menus out onto the page. See a live version here: http://bojacksonselitesports.com/sports-programs/bo-jackson-football

rc-custom-walker

/* ==========================================================================  
	Custom Walker Menu for Secondary Navigation Page Templates
   ========================================================================== */
   
	class Menu_With_Description extends Walker_Nav_Menu {
		function start_el(&$output, $item, $depth, $args) {
			global $wp_query;
			
			$indent = ( $depth ) ? str_repeat( "t", $depth ) : '';
	 
			$class_names = $value = '';
	 
			$classes = empty( $item->classes ) ? array() : (array) $item->classes;
	 
			$class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item ) );
			$class_names = ' class="' . esc_attr( $class_names ) . ' box-wrap one"';
	 
			$output .= $indent . '<li id="menu-item-'. $item->ID . '"' . $value . $class_names .'>';
	 
			$attributes  = ! empty( $item->attr_title ) ? ' title="'  . esc_attr( $item->attr_title ) .'"' : '';
			$attributes .= ! empty( $item->target )     ? ' target="' . esc_attr( $item->target     ) .'"' : '';
			$attributes .= ! empty( $item->xfn )        ? ' rel="'    . esc_attr( $item->xfn        ) .'"' : '';
			$attributes .= ! empty( $item->url )        ? ' href="'   . esc_attr( $item->url        ) .'"' : '';
			$attributes .= ' class="button"';
			
			// get user defined attributes for thumbnail images
			$attr_defaults = array( 'class' => 'nav_thumb' , 'alt' => esc_attr( $item->attr_title ) , 'title' => esc_attr( $item->attr_title ) );
			$attr = isset( $args->thumbnail_attr ) ? $args->thumbnail_attr : '';
			$attr = wp_parse_args( $attr , $attr_defaults );
	 
			$item_output = $args->before;
			
			// box output
			$item_output .= '<div class="box-1">';
			
			// thumbnail image output
			$item_output .= '<div class="thumb">';
			$item_output .= ( isset( $args->thumbnail_link ) && $args->thumbnail_link ) ? '<a' . $attributes . '>' : '';
			$item_output .= apply_filters( 'menu_item_thumbnail' , (isset( $args->thumbnail ) && $args->thumbnail ) ? get_the_post_thumbnail( $item->object_id , ( isset( $args->thumbnail_size ) ) ? $args->thumbnail_size : 'thumbnail' , $attr ) : '' , $item , $args , $depth );	
			//$item_output .= apply_filters( 'menu_item_thumbnail' , (!isset( $args->thumbnail ) && $args->thumbnail ) ? '<img src="'.bloginfo('template_directory').'/images/img-thumb-default.png" alt="Bo Jackson\'s Elite Sports"' : '' , $item , $args , $depth );	
			$item_output .= ( isset( $args->thumbnail_link ) && $args->thumbnail_link ) ? '</a>' : '';
			$item_output .= '</div>';
			
			// title output
			$item_output .= '<h2>';
			$item_output .= apply_filters( 'the_title', $item->title, $item->ID );
			
			// close menu title
			$item_output .= '</h2>';
			
			// menu description output based on depth
			$item_output .= ( $args->desc_depth >= $depth ) ? '<p>' . $item->description . '</p>' : '';
			
			// menu link output
			$item_output .= '<a'. $attributes .'>';
			$item_output .= $args->link_before . 'Details' . $args->link_after;
									
			// close menu link anchor
			$item_output .= '</a>';
			$item_output .= $args->after;
			
			// close box
			$item_output .= '</div>';
			
	 
			$output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
		}
	}


add_filter( 'wp_nav_menu_args' , 'my_add_menu_descriptions' );
  function my_add_menu_descriptions( $args ) {
		if ( ( $args['theme_location'] != 'primary' ) && ( $args['theme_location'] != 'secondary' ) ) {
			$args['walker'] = new Menu_With_Description;
			$args['desc_depth'] = 0;
			$args['thumbnail'] = true;
			$args['thumbnail_link'] = false;
			$args['thumbnail_size'] = 'get-in-the-game';
			$args['thumbnail_attr'] = array( 'class' => 'nav_thumb my_thumb' , 'alt' => get_the_title(), 'title' => get_the_title());
		}
	
		return $args;
	}


/* ==========================================================================  
	Shortcode Setup: Custom Walker Menu
   ========================================================================== */	
	
	// Function that will return our Wordpress menu
	function list_menu($atts, $content = null) {
		extract(shortcode_atts(array(  
			'menu'            => '', 
			'container'       => 'div', 
			'container_class' => '', 
			'container_id'    => '', 
			'menu_class'      => 'menu', 
			'menu_id'         => '',
			'echo'            => true,
			'fallback_cb'     => 'wp_page_menu',
			'before'          => '',
			'after'           => '',
			'link_before'     => '',
			'link_after'      => '',
			'depth'           => 0,
			'walker'          => '',
			'theme_location'  => ''), 
			$atts));
	 
	 
		return wp_nav_menu( array( 
			'menu'            => $menu, 
			'container'       => $container, 
			'container_class' => $container_class, 
			'container_id'    => $container_id, 
			'menu_class'      => $menu_class, 
			'menu_id'         => $menu_id,
			'echo'            => false,
			'fallback_cb'     => $fallback_cb,
			'before'          => $before,
			'after'           => $after,
			'link_before'     => $link_before,
			'link_after'      => $link_after,
			'depth'           => $depth,
			'walker'          => $walker,
			'theme_location'  => $theme_location));
	}
	//Create the shortcode
	add_shortcode("listmenu", "list_menu");
	



/* ==========================================================================  
  Display The Menu (portion goes in your template file)
   ========================================================================== */

  <?php $menu_shortcode = get_post_meta( $post->ID, 'bj_cmb_menu_shortcode', true ); ?>
  	
  <?php echo do_shortcode($menu_shortcode); ?>


/* ==========================================================================  
  From the Admin, the Client can enter this into a custom field and the menu
  will be displayed on the page.
   ========================================================================== */

  [listmenu menu=menu-title-slug]

Matt Try this:

/* ==========================================================================
Custom Walker Menu for Secondary Navigation Page Templates
========================================================================== */

class Menu_With_Description extends Walker_Nav_Menu {
    function start_el(&$output, $item, $depth, $args) {
        global $wp_query;

        $indent = ( $depth ) ? str_repeat( "t", $depth ) : '';

        $class_names = $value = '';

        $classes = empty( $item->classes ) ? array() : (array) $item->classes;

        $class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item ) );
        $class_names = ' class="' . esc_attr( $class_names ) . ' box-wrap one"';

        $output .= $indent . '<li id="menu-item-'. $item->ID . '"' . $value . $class_names .'>';

        $attributes  = ! empty( $item->attr_title ) ? ' title="'  . esc_attr( $item->attr_title ) .'"' : '';
        $attributes .= ! empty( $item->target )     ? ' target="' . esc_attr( $item->target     ) .'"' : '';
        $attributes .= ! empty( $item->xfn )        ? ' rel="'    . esc_attr( $item->xfn        ) .'"' : '';
        //$attributes .= ! empty( $item->url )        ? ' href="'   . esc_attr( $item->url        ) .'"' : '';
        $attributes .= ' data-scroll-nav=';


                   $item_output .= '<a' . $attributes . '>' : '';
                   $item_output .= '</a>' : '';
$output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
    }
}