The characters that can be used in a nickname are determined by the IRC server and it's software, so you'd have to talk to them about that. However, using '*' in a nickname would be a very bad thing for mIRC at least (and probably other clients too) since it's used as a wildcard. Suddenly someone using a script which utilises something like $ial($nick) would break because $ial() would think that you were using a wildcard instead of referring to a specific nick. I doubt EFnet or any other network are going to change the characters allowed simply so people can make their nicks more 'decorative'. Which, when all's said and done, is probably a good thing.