Perhaps you consider yourself an oracle, Mouthpiece of the dead, or of some god or other. (6-7)
The speaker mockingly accuses the statue of thinking it's a high and mighty oracle. All the classical allusions in the poem make us think that she's specifically referencing the Oracle of Delphi. Of course, the priestesses of that oracle were said to get the scoop on the future from their god, Apollo, not the spirits of the dead.
To mend the immense skull-plates and clear (14)
The speaker could have chosen to talk about mending the statue's head, but instead chooses the word "skull-plates." This brings a deathly image to our minds and seems to hint at the idea that this fallen Colossus is meant to represent a human who's died.
The bald, white tumuli of your eyes. (15)
The speaker slips in a slick reference to death by comparing the statue's eyes to "tumuli," which is a fancy-shmancy word for a burial mound. Here again, she seems to be subtly telling us that this statue represents a human being who's died.