Details please realize that the additional field may be written bb code.
This will need to relink pages galleries. Thank you :)
Αndrй please help and then have tried everything :)
Open displayimage.php, find
$info[$CONFIG['user_field' . $i . '_name']] = make_clickable($CURRENT_PIC_DATA['user' . $i]);
and replace with
$info[$CONFIG['user_field' . $i . '_name']] = make_clickable(bb_decode($CURRENT_PIC_DATA['user' . $i]));
(not tested).
Thank you ΑndrĂ©, works great!
It turns out it was all so simple :D