These bonuses are ones included in the Kuro and Shiro editions of the game in Japan, so fans in the far east don't have to be green with envy. In addition, GameStop pre-orders will get a Dynamic Hostess theme for their PlayStation 3, on the apparent (and probably correct) assumption that GameStop shoppers are also the guys who would like to ogle virtual ladies.
The trend of adding one-time codes to entice new game sales has become so commonplace after the success of EA's Project Ten Dollar that it's virtually expected now. If you pick up a new game, you'll almost certainly get goodies to go with it. If you shop for new games anyway, like I do, this is a welcome bit of bribery.