In that artwork...
The children of God standing above the illusion of authority or the material world/governments/money could simply logically mean they are spiritually/in their hearts above the subjugation to fearing the rise and fall of nations...
But alas, it's art... it can mean whatever you want it to...
But the twin towers being in the artwork need not cause for more fear... it might very well debunk any notion that the artwork is a guaranteed accurate prophecy... but again, whatever you want... it's art.
"But of that day and that hour knoweth no man, no, not the angels which are in heaven, neither the Son, but the Father."
-St. Mark

