I don't think unoriginality should be mistaken for "style".
A re-occuring theme in an artists work can most definitely be noted as the artist's style. The "White Trash" characters, and their dialogue, is as much Zombie's style as Sam Raimi's trademark camera work is his.
I would love to hear his song Lords of Salem play during the end credits.
The song would fit well, with the bleak ending.
I'm actually very interested in seeing how he incorporates the song as well. I remember back when House of a 1000 Corpses came out, I was never really a fan of the song until I saw it used within the movie. I have a feeling this may be a similar case.