I don't think the art book is well known at all. It's hard to find and only in japanese. I think people are cosplaying the peacock dress because they've seen how well yours turned out. ^^ Actually most of them don't know about the art book and choose the colours randomly. It's a very plain outfit unless you change it anyways.

More popular series have far more cosplayers. Maybe we can get things to go the other way. By cosplaying a series will get it more attention? Maybe if we cosplay enough we'll get PSOH a real anime series someday! ^^;