I think it's a pre-order bonus, but I received it anyways because there were more cards then pre-orders. I also bought it in Japan. The trading card I received is of Sasari and the password to unlock the free wallpaper on the site is 5247 - 3115. Input it here
http://phantasystar.sega.jp/pszero/download.php then press the next arrow to receive the wallpaper.
Additionally, the password above can be used to recieve a special guest item from the Sewer Vending Machine. This particular one is called Valiant from a manga known as Blazer Drive.
Here are the others:
Selvaria Spear from Valkyria Chronicles (PS3) 4137 5476
Valiant Mysticker from Blazer Drive (manga) 5247 3115
Seena KanonÂ’s Blade Cannon from Shining Wind (PS2) 3489 9723
Hatsune MikuÂ’s leek from Hatsune Miku -Project Diva- (PSP) 8331 7716
Additionally, you can input those on the website to get wallpapers too; however, they are of all the same image, I think.
I'm at level 5. Just beat the first stage. Nearly died against the boss! Is it me or is the targeting system not as good as in PSO? I just might not be used to it yet.
Edit: You can see the cards here
http://**********.com/?p=61236
Also, there was a launch party for the game today in various places all over Tokyo. I just found out today. I wish I'd gone in case they were giving away a promotional item.
Edit 2: Ok I'm at Level 9 now. Played for about two hours - one hour online and the other offline. I've played through two stages so far and I have to say, these levels are about the equivalent of say Forest 1 or Cave 1 but that's it. In PSO there would be three levels for the forest or four levels for the caves but in PSZero these first two (of seven) areas only have one level. I hope the other areas are a lot longer; elsewise, this would be a pretty short game which I can't really see myself playing for as long as PSO Episode 1.