Where is theThe Comment Form Template?
It is in the default comment module , and editing the core options is not a good practice at all.

You can alter the comment  form in your active theme template.php or hook_form_alter() function in your custom module 

&lt;?php 
function THEMENAME_form_comment_form_alter(&amp;$form, &amp;$form_state) {
        //dpm($form); //shows original $form array 
        //$form['author']['#type'] = 'fieldset'; 
       // $form['author']['#title'] = 'Your Information'; 
       // $form['author']['#collapsible'] = FALSE; 
      //  $form['your_comment'] = array( '#type' =&gt; 'fieldset', '#title' =&gt; t('Your Comment'), '#collapsible' =&gt; FALSE, '#weight' =&gt; 2, ); 
        //Subject 
       // $form['your_comment']['subject'] = $form['subject']; 
       // unset($form['subject']); 
     //   $form['your_comment']['subject']['#weight'] = -10; 
        //Comment 
        $form['your_comment']['comment_body']['#prefix'] = "&lt;div&gt;User picture&lt;/div&gt;" ;
        $form['your_comment']['comment_body'] = $form['comment_body']; 


}
?&gt;


You can add user picture using prefix/suffix in the comment form.
Try if it work for you.