The powers of a person come into rule when the higher awareness is enthroned inside. To be beheaded for the witness is to lose the reasoning surface mind, the head that argues and doubts, so the deeper knowing can govern in its place. Those who never took the mark of the beast are the states in a person that never surrendered thought and action to the animal, sense-bound nature. Freed from that lower rule, they share in the long, full reign of the awakened life.
The forehead and the hand are where mind and deed are stamped; the mark not received means neither the thinking nor the doing was owned by the lower self. When the animal nature no longer stamps thought and act, the higher life governs from within.
Thrones: the seats of inner authority a person comes to occupy when the higher awareness rules
Beast: the animal, sense-bound nature that seeks to govern thought and action
Mark: the claiming of the mind and the deeds by the lower nature, stamped where a person thinks and acts
Forehead: the place of thought, where the governing self is marked
Hand: the place of action, where the governing self is marked
1000 years: the number of fullness and completion, the whole undivided reign of the awakened life