webbed-site/_includes/layout/gallery/art.html

<div class ="image-gallery" style="margin: auto;">
  {% assign sorted = site.static_files | sort: 'date' | reverse %}
  {% for file in sorted %}
  {% if file.path contains page.imgurl %}
  {% if file.extname == '.png' or
    file.extname == '.jpg' or
    file.extname == '.gif' %}
    {% assign filenameparts = file.path | split: "/" %}
      {% assign filename = filenameparts | last | replace: file.extname,"" %}
      <div class="box"><a href="{{ file.path | relative_url }}" title="{{ filename }}">
        <img src="{{ page.thumbsurl }}{{file.name }}" alt="{{ filename }}"  class="img-gallery" />
      </a></div>
      {% endif %}
    {% endif %}
  {% endfor %}
</div>