Here's the new cast members for season two. Most of the cast seems spot on for their role, but a few seem a bit "off" to me. Most notably casting a British model as the part of Brienne seems way fucked up. Oh well, it will still be an awesome fucking season. This contains no spoilers, but it does give a bit of background on the new characters.
Game of Thrones: Who's Who in Season 2 - TV Feature at IGN
Here's another trailer.