wp_nav_menu: output featured image of each page listing

Honestly I have not used wp-nav-menu much other than just using it for a menu. I am thinking in your case it might be more semantic to create a custom-post-type for “Projects” and then list those (rather than using the wp-menu as a Project sorter)
. You can use the plugin “Post Types Order” to order your custom posts the way you want (works the same as arranging the order of menus..with a drag and drop).

The advantage to using Custom Post Types is that there is a lot more flexibility to use them how you want.
So, in short:

  • Create a custom post type for “Projects”
  • Install Post Types Order to order your Projects
  • On the page (or sidebar) where you want to list your projects use the code below, add the following snippet.

$example = new WP_Query( 'post_type' => 'projects','showposts' => '20' );
// gives the title for each project
if ( $example->have_posts() ) : 
    while ( $example->have_posts() ) : 
    the_post(); 
    ?>
    <div class="project" >  
        <!-- thumbnail -->
        <span class="project-thumb">   
            <?php the_post_thumbnail(); ?>
        </span>
        <!-- end thumbnail -->
        <h4><?php the_title(); ?></h4><!--title -->
    </div><!--#project -->
    <?php 
    endwhile; 
endif;