Add class to views row if image fields has content
When you use the preprocess function you find the result in 

$vars['view']-&gt;result


and the corresponding classes array under 

$vars['classes_array']


where in results and in classes array the corresponding rows have the same key.

You can do now something like this in your preprocess function:

foreach ($vars['view']-&gt;result as $rid =&gt; $row) {
  if (isset($row-&gt;YOUR_FIELD) &amp;&amp; !empty($row-&gt;YOUR_FIELD)) {
    $vars['classes_array'][$rid][] = 'has_field';
  }  
  else {
    $vars['classes_array'][$rid][] = 'has_no_field';
  }
}


It is untested and just a little scribble but maybe it helps you.