I wish I could say we are looking into things too much, and that it's just Harry's affinity with fire - but that's not very like Butcher's style. It could be something similar to what Harry saw in Molly, though - paths, choices, maybe a Harry in white knightly armor, a gray Harry as he is then and there, and a Dark Harry with the goatee in all, shrouded in flames. Jim did say that Harry was on a darker path, after all.