If the shadow reflects the negative bits of oneself, then I still think Draco is Harry's shadow. It has been mentioned before, but I think Luna is Hermione's shadow, and Crabbe/Goyle are Ron's shadow. Luna might seem an odd choice, but we've talked about how her faith contradicts Hermione's dedication to reason; I think blind belief in such things is something Hermione would definitely dislike about herself. And Crabbe/Goyle are loyal to Draco to the point of mindless drones; I would imagine that Ron might fear becoming such a friend at times, but I think he has managed to support Harry but stand his own farily well thus far (I would cite his taking over the chess game in PS/SS, his intuition about Crookshanks in PoA, his anger in GoF, and his doubt of Malfoy in HBP, among other things.)

I think Snape is most likely the shadow of James and Sirius, and not Harry; but I might also entertain the idea of him being the shadow to Dumbledore of Voldemort. However, I don't have the time to discuss it at the moment, so I will sleep on it and see what you all come up with in the meantime on that one.