I think it's just for the standard edition, they didn't get any of the other editions(theres like 4 or 5 different steelbook editions exclusive to other sites with their own DLC characters). The only preorder bonus I saw was for
a free t-shirt and something else that I cannot remember instore.
I pre-ordered in my local gamestation....game only cost £40 for me despite being advertised for £44.99..was the Robin edition, also came with a free comic which is 1 of a 5 part run which tells the story from after Arkham Asylum leading into Arkham City.
Game also had a holographic cover Sleeve showing Bats and Robin