As I understand it, the point is to promote questions for subjects that are not usually asked about.
But who actually picks the themes? Because currently we have nationalism, then we'll have Canada, and finally the 1970s. I have personally seen a fair number of previous questions on these subjects, but so far I've never seen a single question for, idk, the Indian Ocean trade or the Great Lakes kingdoms of Africa.
How can I suggest new themes?
I mean, one way to go about seeing that question is to ask it:) The weekly themes are simply a suggestion the way I understand it - actually, now I think of it, it would be nice to have a single thread in the Sunday Digest to collect all the answers to the weekly topic questions. I might go ahead and try to do that...uh, next week:) Also, if you shoot the mods a message, I'm sure they'd be totally OK with suggestions.
There is a rough list we draw on of ideas submitted, and pick randomly from. If you have ideas, best place to submit them is as a reply to the thread that goes up each week to announce the new theme.
We’ve generally appointed one or more mods to each theme day, and those moderators have wide discretion to choose questions, sometimes with discussion with the rest of the team and/or the Panel of Historians, and sometimes on their own. In particular, they’re sometimes scheduled in advance if we know someone’s taking a research trip or doing fieldwork. We also take questions on occasion that would otherwise be rule-breaking and turn them into our Trivia theme.
If you have ideas of questions you'd like to see, feel free to message the mods and let us know! Or if you'd like to see us re-run an older question, we can look into that too.
edit: It looks like I misinterpreted what the OP was asking about -- I was answering for the daily themed threads. Sorry about that, but now you know how our themed threads work!
As /u/LukeInTheSkyWith says, drop a suggestion in the weekly announcement. Also feel free to PM me, and I'll add them to the list.