Profile Pictures in Inbox

I’ve been trying to figure out how to place a profile picture of the initial sender next to each thread in the inbox. Although it seems there has been some discussion of theming individual threads through modification of the privatemsg-view.tpl.php file, I can’t find many (if any) threads detailing how to create a new column in the Inbox view.

The module documentation is fairly good on the subject, and from that I’ve pieced together the following:

1. I need to create a new SQL query to grab the author picture.
   

   function privatemsg_sql_picture(&$fragments, $uid) {
     // Set the primary table.
     $fragments['primary_table'] = '{users} users';
   
     // Add a field.
     $fragments['select'][] = 'users.picture';
     
     // Join another table.
     //$fragment['inner_join'][] = 'JOIN pm_message ON (users.uid = pm_message.author)';
   
     // And finally add a condition.
     $fragments['where'][] = 'users.uid = %d';
     $fragments['query_args']['where'][] = $uid;
   }
   

2. I need to create a call in the format phptemplate_privatemsg_list_header__fieldname to generate the column headers
   

   function phptemplate_privatemsg_list_header__picture() {
     return array(
       'data'    => t('Author'),
       'key'     => 'picture',
       'class'   => 'privatemsg-header-author_picture',
       '#weight' => -45,
     );
   }
   

3. I need to create a call in the format phptemplate_privatemsg_list_field__fieldname to generate the column content in each row
   

   function phptemplate_privatemsg_list_field__picture($thread) {
     $field = array();
     $field['data'] = $thread['picture'];
     $field['class'] = 'privatemsg-list-picture';
     return $field;
   }
   

Right now, I'm putting all the code into template.php.

I'm not quite sure where/how I'm supposed to call the privatemsg_sql_picture function. The docs give the following:

$query = _privatemsg_assemble_query('getsubject', 5);
$result = db_query($query['query']);

...but I'm unclear on where I'd call it (privatemsg seems to assemble queries when it is loading individual threads in the privatemsg_thread_load function).

Is this the correct approach, or am I pursuing a dead end? I'm not 100% clear if the documentation is referring to the creation of new columns in the Inbox view or in the individual thread view (it seems that the later case would be handled easily by creating a customized .tpl.php). I’d greatly appreciate it if someone could point me in the right direction on this. I’d love to do a tutorial on the process once I figure it out, I’m surprised I haven't found someone else asking about it.