I just wanted to throw something out there!
So this is my theory about good omens:
In season one episode one Aziraphele gave Adam and Eve a flaming sword. Michael, the Archangel carries a flaming sword.
And Crowley, the fallen angel, spoiler for season two, has full access to all of heavens library, some thing only a higher up Angel has access to and was cast down.
So my theory is that Aziraphele is Michael and Crowley is Lucifer!!