Who is on the covers of the books?
City of Bones: Jace
City of Ashes: Clary
City of Glass: Sebastian *
City of Fallen Angels: Clary and Simon
City of Lost Souls: Clary and Jace
City of Heavenly Fire: ?
Clockwork Angel: Will
Clockwork Prince: Jem
Clockwork Princess: Tessa
* In answer to the often asked question “Why does Sebastian have wings on the cover of City of Glass?” : Because in City of Ashes, when Clary prophetically dreams about him (p. 184 in my hardback American copy of Ashes), he has wings. Black ones, covered in blood. Wings are not a sign of inherent goodness; fallen angels have them too. 
City of Ashes, p. 184: ” It was Jace, all in burning gold with his gold eyes and gold hair, and
white-gold wings sprouted from his back, wider and more thickly feathered than any bird’s.
He smiled like a cat and pointed behind her, and Clary turned to see that a dark-haired boy was standing
there, and wings spread from his back as well, feathered black as midnight, and each feather was
tipped with blood.”
