I'm not sure of one which comes with a Finnish language pack but you could translate your own.
I'm pretty sure that rvskin don't allow you to alter the language files so creating your own based on their's is out of the question.
I know that the default themes which ship with cPanel are not yet fully language aware so don't waste your time translating one of their language files.
I would suggest that you purchase one of the themes from www.cpskins.com. These are fully language aware and I believe they ship with English and Portuguese. You can translate one of these by simply creating a new language file based off one of the others. You could also see if cpskins want to make a deal with you in return for providing them with the Finnish language file when complete so they can add it to their skins (not sure if they're open to this but worth a try).
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