Problem adding Flexslider

Hi,
I’m trying to get a flexslider working on a single post page (all the attachments of the post should go in the slider). I’m now setting up the flexslider with direct links to images to test it but I can’t get the slider to work properly. This is what I’ve done:

in my Functions.php file I added:

//Flexslider CSS
function theme_styles() {
	wp_enqueue_style('flexslider',get_template_directory_uri().'/css/flexslider.css');
}
add_action ('wp_enqueue_scripts','theme_styles');

//Flexslider js
function theme_js() {
	wp_enqueue_script('jquery.flexslider-min',get_template_directory_uri().'/js/flexslider.js', array('jquery'),'',true);
	wp_enqueue_script('theme_js',get_template_directory_uri().'/js/theme_js.js', array('jquery'),'', true );
}
add_action('wp_enqueue_scripts','theme_js');

I get the flexslider files linked in my footer.
To just test it I added the following to my single post:

<div class="flexslider">
  <ul class="slides">
    <li>
      <img src="...dummydirectory/bg_coming_soon.jpg" />
    </li>
    <li>
      <img src="...dummydirectory/bg_coming_soon.jpg" />
    </li>
    <li>
      <img src="...dummydirectory/bg_coming_soon.jpg" />
    </li>
    <li>
      <img src="...dummydirectory/bg_coming_soon.jpg" />
    </li>
  </ul>
</div>

When I go to the page I see the the slider is loaded (with correct css styles) but none of the images are showing. So I actually receive a small container (full width) with a really small height and no images…

Does someone see what I’m doing wrong here?

Thanks!