I used in-line styling
Code:
<div class="product_thumb ">
<a href="javascript:void(0)">
<img style="margin-top:0;" src="http://cdn.shopify.com/s/files/1/0174/5504/products/action-form-medium-144_small.jpg?4889" alt="Adjustoform Action Form Mannequin Size 16 - 22" rel="lightbox-images">
</a>
</div>
But it would be better to add a class for vertical images that do this in the css