Pretty interesting stuff.
The two most up for interpretation, in my opinion, are "A corpse stood at the prow of a ship, eyes bright in his dead face, grey lips smiling sadly" and "From a smoking tower, a great stone beast took wing, breathing shadow fire."
Grey lips smiling sadly doesn't sound like a Greyjoy to me... I'd lean towards Connington. His presumed death "corpse", and worsening greyscale fits the rest pretty well. Of course I suppose it could be more of a literal corpse, any wight would fit the description well if they were sentient (Coldhands maybe?) Though, I suppose the ship element does lean back towards Victarion.
The smoking tower though... that's vague. I'm not sure I like the theories involving stone dragons - Daenerys knows what a dragon looks like, why would it be described as a beast? Perhaps Catelyn Stark as Stoneheart? Certainly stone, and somewhat of a beast, though the shadow part and smoking tower are hard to explain. Blackfyre? Black Flame (Moqorro as named by Victarion's crew)?
It seems like no matter how they're interpreted there are some elements unexplained.