Yes you can easily add xfield image in quick search, simply open
/engine/ajax/search.php and find:
$db->query("SELECT id, short_story, title, date, alt_name, category FROM " . PREFIX . "_post WHERE " . PREFIX . "_post.approve=1".$this_date." AND (short_story LIKE '%{$query}%' OR full_story LIKE '%{$query}%' OR xfields LIKE '%{$query}%' OR title LIKE '%{$query}%') ORDER by date DESC LIMIT 5");
Replace with:
$db->query("SELECT id, short_story, title, date, xfields, alt_name, category FROM " . PREFIX . "_post WHERE " . PREFIX . "_post.approve=1".$this_date." AND (short_story LIKE '%{$query}%' OR full_story LIKE '%{$query}%' OR xfields LIKE '%{$query}%' OR title LIKE '%{$query}%') ORDER by date DESC LIMIT 5");
Find:
$description = preg_replace( "'\[attachment=(.*?)\]'si", "", $description );
Add below:
$xfieldsdata = xfieldsdataload( $row['xfields'] );
Now you can add image tag in quick search by find the line:
$buffer .= "<span>".$description."</span></a>";
Replace with:
$buffer .= "<span><img src=\"".$xfieldsdata['Name of your additional fields']."\" class=\"poster\" style=\"float:left;margin:5px;width:"50px;height:50px\" />".$description."</span></a>";
You must replace "Name of your additional fields" with your actual xfield name and adjust the size of your choice...
This hack has been tested with DLE 9.8 and newer.