Flexslider field: number of thumbs, number photos and thumb slider
I ended up doing it from scratch. I created a custom node.tpl.php, got all the pictures with

$photos = field_get_items('node', $node, 'field_photos');


Then looping through all items and creating for each item the options

$photos_slide = array(
    'style_name'    =&gt; 'large',
    'path'          =&gt; $photo['uri'],
    'width'         =&gt; '',
    'height'        =&gt; '',
    'alt'           =&gt; '',
    'title'         =&gt; $title,
);


and then print the image:

print theme('image_style', $photos_slide);


You can follow this example http://flexslider.woothemes.com/thumbnail-slider.html in order to know how to set the HTML.