Smiley question.

Hy! I really like the punBB forum, but a have a little problem! A would like to add some new smiley, that are bigger then the standarts. I notesed that all the standart smileys ar 15x15 px. Ok, I can change them from parser.php, but them all of them will change, and that would look terible... is there any way to add like each smiley with diferent size??
tnx!