Typo3 and Fluid-Templates: use Mediafield from Pagesettings in Menu
{namespace v=Tx_Vhs_ViewHelpers}
<nav class="image-nav clearfix">
<v:page.menu.directory pages="{page.uid}">
<f:for each="{menu}" as="item">
<div class="image-nav-item">
<f:link.page pageUid="{item.uid}"
title="{item.title}"
class="{f:if(condition: item.active, then: ' active', else: '')}">
<div class="image-nav-title">
{item.title}
</div>
<v:page.resources.fal table="pages" field="media" uid="{item.uid}" as="images">
{images -> v:iterator.first() -> v:variable.set(name: 'image')}
<f:if condition="{v:media.exists(then: '1', else: '', file: '{image.url}')}">
<f:then>
<f:image src="{image.url}" alt="{image.alternative}{f:if(condition: image.description, then: ' {image.description}', else: '')}" class="img-responsive" width="214" />
</f:then>
<f:else>
<f:image src="/fileadmin/user_upload/dummy-nav.jpg" alt="{image.alternative}{f:if(condition: image.description, then: ' {image.description}', else: '')}" class="img-responsive" width="214" />
</f:else>
</f:if>
</v:page.resources.fal>
</f:link.page>
</div>
</f:for>
</v:page.menu.directory>
</nav>