Where is it stored?...I remember using iChat for the first time and it just placed my current icon, that, i thought I lost in the first place! Weird...
i have no idea where ichat stores your icon. but you can just click on the icon box on your buddy list and paste any image in, and resize it accordingly
I've had trouble making this work; for some screen names, iChat insists on using whatever icon it first used. iChat for me has been, on the whole, unreliable.