You can pull a firework effect just by using subtype 1 in the string packet with a 4 letter or longer word (might work with a shorter word, I just remember using a 4 letter word).
Edit: Oh, I thought you were looking for the effect to display it on your client. I couldn't find it in c3 either. Don't take my word for it, but maybe it's in a wdf file. Did you look at other sources that have fireworks to see what effect they were using?
You can view dds thumbnails using this btw:
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