No .. that is currently not possible

sorry but i found a way to have different smileys there.

find the smileys you want to use ie: Dizzy Smileys from smf,download the zip,rar file and extract,once extracted you should have a folder called dizzy_light.
upload the dizzy_light folder to root dir /Smileys with an ftp program,ie: filezilla.

find your shoutbox.php file in /Sources/PortaMx/Class
open up shoutbox.php file with notepad/word/dream weaver or your preferred program

search for,setup the PortaMx smileys,it may be online 331 for you,if you want the same one as i,have use code below,or change to custom ones.
$codes = array(':)', ';)', ':D', ';D', '>:(', ':(', ':o', '8)', '???', '::)', ':P', ':-[', ':-X', ':-\\\\', ':-*', ':\\\'(', '>:D', '^-^', ':))', 'O0', 'O:-)', '??(', 'C:-)');
$files = array('smiley', 'wink', 'cheesy', 'grin', 'angry', 'sad', 'shocked', 'cool', 'huh', 'rolleyes', 'tongue', 'embarrassed', 'lipsrsealed', 'undecided', 'kiss', 'cry', 'evil', 'azn', 'laugh', 'afro', 'angel', 'blank', 'police');
once them changes has been made there is two more change needed

find
$smPath = $modSettings['smileys_url'] . '/PortaMx/';replace
$smPath = $modSettings['smileys_url'] . '/dizzy_light/';
find
foreach($this->smileys as $sm)maybe on line 379

and edit the first <div style="height:30px;">'; to <div style="height:100px;">';
maybe on line 387
this will keep the box in shape


this is how i got mine to work,hope this will help others who would like to have a change now and again.

i have made a slight adjustment to the above...

Bad that you can not use a standard set of SMF Smileys