mediaconvert/templates/blocks/media-item.html

{% load thumbnail %}
        <li class="col-md-4 col-sm-6">
        <div class="well">
            <a class="poster-link" href="{{item.permalink}}"><img class="u-photo" src="/media/{% thumbnail item.poster.image 200x200 %}" /></a>
            <h3><a href="{{item.permalink}}">{{item.title}}</a></h3>
            <p>{{item.description}}</p>
        </div>
        </li>