AddEmbeddedImage($path, $cid, $name = "", $encoding = "base64",
$type = "application/octet-stream")
Cita:
Iniciado por phpMailer Make sure to set the $type to an image type. For JPEG images use "image/jpeg" and for GIF images use "image/gif".
Código PHP:
$pathImage = "http://www.xxxx.com/pub/voto/20081024101008.jpg";
$cid = 'mi foto';
$mail->AddEmbeddedImage($pathImage,$cid,$cid,'base64','image/jpeg' );
fijate de esta forma por las dudas