1. If you don't even know what topic area interests you by now, maybe you shouldn't be an advanced PhD student. Were there perhaps some courses that you liked? Or have you ever attended an interesting seminar?

2. In every research-oriented business school that I know, a PhD student would be a candidate for a degree from a particular department (and be subject to that department's requirements or at least the requirements of some particular interdisciplinary program to which the student has been formally admitted) rather than "anything but accounting."

3. Rather than seeking anonymous advice here, you should talk to your advisor and other faculty members.