Two more decks have been added to Magic: The Gathering - Duels of the Planeswalkers 2012 today in the second expansion for the game. The decks will be available to use in both the campaign and multiplayer games. There aren't any additional achievements, I'm afraid.
Explore two brand-new decks and expand your mastery of Duels of the Planeswalkers 2012. Includes “March to War,” a red and white deck featuring an army of brutally efficient Soldiers, and “Ghoulkeeper,” a vile black deck featuring an unrelenting Zombie legion. Both decks are available for Campaign and Multiplayer play.The "Magic 2012 Deck Pack 1" costs 240 MSP and can be downloaded from here. Those of you who don't want to download the expansion pack will need to download the free compatibility pack if you want to continue to play against those players with the new content; that pack can be downloaded from here.
We've got the full list of Magic: The Gathering - Duels of the Planeswalkers 2012 achievements - check the list for guides to unlocking them.