normally it's indeed the file default_events_table in common folder unless the option for responsive tmpl was ticked.
There should be a setting to display images in the table. it's within the settings-view | layout settings.
<?php if ($this->jemsettings->showeventimage == 1) : ?>
<td headers="jem_eventimage" align="left" valign="top">
<?php if (!empty($row->datimage)) : ?>
<?php
$dimage = JemImage::flyercreator($row->datimage, 'event');
echo JemOutput::flyer($row, $dimage, 'event');
?>
<?php endif; ?>
</td>
<?php endif; ?>
--> How is the image entry in the database-table?
--> something that can be done is to remove the if statements (display without check if setting for imagedisplay was ticked) to see if it makes a difference or maybe you've an error somewhere.