title: Schema.org: using ImageGallery with ImageObject?
body: <p>I've started to use schemas from <a href="http://schema.org/" rel="nofollow">schema.org</a> in my HTML code and have prepared an image gallery (snippet below).  When I pasted my code into <a href="http://www.google.com/webmasters/tools/richsnippets" rel="nofollow">Google Structured Data Testing Tool</a>, I received no errors, thus I assumed my way use of these schemas was proper, but am still if it is.  Is it?</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;figure itemscope itemtype="http://schema.org/ImageGallery"&gt;
    &lt;figcaption itemprop="description"&gt;The castle through the ages: 1423, 1858, and 1999 respectively.&lt;/figcaption&gt;
    &lt;figure itemprop="image" itemscope itemtype="http://schema.org/ImageObject"&gt;
      &lt;figcaption itemprop="caption"&gt;Etching. Anonymous, ca. 1423.&lt;/figcaption&gt;
      &lt;a href="castle1423.jpeg" itemprop="contentURL"&gt; &lt;img src="castle1423_thumb.jpeg" alt="The castle has one tower, and a tall wall around it." itemprop="thumbnailUrl"&gt; &lt;/a&gt; &lt;/figure&gt;
    &lt;figure itemprop="image" itemscope itemtype="http://schema.org/ImageObject"&gt;
      &lt;figcaption itemprop="caption"&gt;Oil-based paint on canvas. Maria Towle, 1858.&lt;/figcaption&gt;
      &lt;a href="castle185.jpeg" itemprop="contentURL"&gt; &lt;img src="castle1858_thumb.jpeg" alt="The castle now has two towers and two walls." itemprop="thumbnailUrl"&gt; &lt;/a&gt; &lt;/figure&gt;
    &lt;figure itemprop="image" itemscope itemtype="http://schema.org/ImageObject"&gt;
      &lt;figcaption itemprop="caption"&gt;Film photograph. Peter Jankle, 1999.&lt;/figcaption&gt;
      &lt;a href="castle1999.jpeg" itemprop="contentURL"&gt; &lt;img src="castle1999_thumb.jpeg" alt="The castle lies in ruins, the original tower all that remains in one piece." itemprop="thumbnailUrl"&gt; &lt;/a&gt; &lt;/figure&gt;
  &lt;/figure&gt;
  </code></pre>