To my knowledge, there are currently no rules for silver weapons. Silver is not listed in the Special Materials section.
There was
a discussion over on the Witch Hunter forums about silver weapons. And although it's a very different setting, some of the discussion seems fitting. Silver is really a horrible metal for most weapons. It's very soft and expensive. There are methods by which some amount of silver could be used in a weapon (alloys, fuller grooves, electroplating, etc.) but that's all pure speculation about whether or not silvered weapons are viable in this particular fantasy setting.
If you're just looking for a schtick, then I'd say pay for a fine or Exceptional weapon and describe it as having silvered inlay. If you're looking for what kind of in-game benefits a silvered weapon would have, then I don't believe that there are any rules for that.
Hope that answers your question.
Scott
p.s. I would expect silver bullets to be completely viable in Arcanis... horrendously expensive, but just as viable as the (presumably) lead shot that is commonly used.