How do I render an image from a Twig template?
you could just use {{ content.field_image }}

Here is an example of a template file from a paragraph

{%
  set classes = [
  'paragraph',
  'paragraph--type--' ~ paragraph.bundle|clean_class,
  view_mode ? 'paragraph--view-mode--' ~ view_mode|clean_class,
]
%}
{% block paragraph %}
&lt;div{{ attributes.addClass(classes) }}&gt;
  {% block content %}
      &lt;div class="row collapse expanded mainsection"&gt;
        &lt;div class="large-12 columns"&gt;
          &lt;div class="row collapse"&gt;
            &lt;div class="large-12 columns"&gt;
              {{ content.image }}
            &lt;/div&gt;
          &lt;/div&gt;
        &lt;/div&gt;
      &lt;/div&gt;
  {% endblock %}
  &lt;/div&gt;
{% endblock paragraph %}


Notice that I only need to write {{ content.FIELDNAME }}, if I wrap everything in a {% block content %}