How to Create a Image Field Template
Quick and dirty, if all you are wanting to accomplish is to add class="img-rounded" to the &lt;img&gt; tag, you could do this right before you render $item:

&lt;?php $item['#item']['attributes']['class']='img-rounded'; ?&gt;


(Quick and dirty because this assumes no one else somewhere along the line has added or will be adding a class to your image.)