A group called the Coup also had that on their album cover before 9/11....consider though, that there was a previous attack on the WTC before 9/11. Remember the Biggie lyric where he's all "blow up like the world trade!" I think these were all references to the first attack and/or metiphors for the likely destruction of America's financial structure, using the WTC as the icon for US financial affluency and power being destroyed.