You can change the position of <div class="catimg"> into h2 tag.
Open /components/com_jem/views/categories/tmp/default.php, Go to line 34 and move this block into <h2> tag previous.
<?php foreach ($this->rows as $row) : ?>
<h2 class="jem cat<?php echo $row->id; ?>">
<?php if ($this->jemsettings->discatheader) { ?>
<div class="catimg">
<?php // flyer
if (empty($row->image)) {
$jemsettings = JemHelper::config();
$imgattribs = $jemsettings->imagewidth;
$imgattribs = $jemsettings->imagehight;
echo JHtml::_('image', 'com_jem/noimage.png', $row->catname, $imgattribs, true);
} else {
$cimage = JemImage::flyercreator($row->image, 'category');
echo JemOutput::flyer($row, $cimage, 'category');
}
?>
</div>
<?php echo JHtml::_('link', JRoute::_($row->linktarget), $this->escape($row->catname)); ?>
</h2>