I am currently writing my PhD dissertation and was wondering in what order I should list committee members in my dissertation? What is a good order that does not offend anyone? I know the advisor has to be listed first. For the rest of the members, some of the options I considered were: (a) listing by decreasing order of seniority, (b) alphabetical, (c) list external last. The problem with (a) is that the senior most professor is an external (from a different university) and comes up before Profs from my own department. The problem with (b) and (c) are that the senior most person, who is also quite famous, now comes last. Am I overthinking this?
Probably you are overthinking it. If they have different roles you can list them with their role and avoid ordering problems. Otherwise I'd consider alphabetical.
I'll admit that in some fields there may be a tradition about how to do it, but I've never heard of that. And note that in some circles the one listed last is considered the most prominent. It is hard to really draw conclusions, hence alphabetical.
And, your advisor might have some good advice about this.
Besides asking your adviser, you could look at some of the recent dissertations written in your department to see whether a specific format tends to be used. Print copies of the dissertations are probably shelved somewhere in your university library (and/or you might have access to digital versions using your university library), and copies might also be in your department library, department reading room, department common room, etc. (if any of these exist).
I suggest checking with the graduate school administration of your university (not just your department). There may be amazingly specific rules about the format of your dissertation, including the list of committee members. For example, in my university, the title page of a doctoral dissertation must say that it's "submitted to The University of Michigan" with a capital "T" in "The". I think the committee members are listed with the adviser first (labeled not as adviser but as chair of the committee) and then the other members in alphabetical order; I don't guarantee that, though, since I never paid much attention to the ordering of the list.