blog/_src/_includes/relatedphotos.html

<aside class="related-photos">

    <div class="grid grid--gutters grid--half grid-medium--third">

        {% for post in site.categories['photos'] limit:9 %}

            <article class="related-photo grid__col">
                <a class="photo-link" href="{{ post.url }}">
                    {% include picture.html size='photothumb' file=post.image %}
                </a>
            </article>

        {% endfor %}

    </div>

</aside>