This is a very self-indulgent answer, but... the viking age, perhaps?
Okay, honestly I'd just like some more content of it in general, there barely even exists any custom content of it. I actually just want more CC of this time period and place, it does not need to be an official pack. I'm Norwegian, old norse culture is just my heritage. And I have a few viking characters.
A more general answer that would cover the wishes of a more general audience would be the medieval age. That would be neat too!
The 1800s would also be cool, though I do feel like we already got some of it through Vampires, probably.
Ever since I got more interested in vampires, I also got more interested in history as a result, and honestly, anything that takes place like 100+ years ago would be pretty neat to have.
Also, if there was a dedicated pack to an older time period like this, it could also mean that not everyone has to have a phone automatically anymore. Currently, sims just act too... modern. They pull out their phones as an idle animation, and they gain the gaming skill autonomously, which is incredibly annoying. The game without mods is just explicitly set in the modern age, the present.