If it interests you, I had a Finnish Pagan-themed update for VIET ages ago, that added features and flavor for the Finnish Pagans (you can see the dev diaries (
here and
here) I had on them, though they're slightly outdated). Feel free to take from it what you want.
I also had some West African map changes, including Takrur, that I removed for the current version of VIET, though I'll be reintroducing them at a later time (
here is what they looked like; a future version will likely be different); you may be interested in that, just ask me if you want to look at the files. Additionally you may want to ask the SWMH team if they can show you some of the resources they used for the African portions of their map, they did considerable research for the region and will likely be more than happy to share their sources. And, if you're interested in West African flavor and mechanics, feel free again to borrow from VIET if you like any of it; I consider my West African themed update my current magnum opus of VIET's themed updates.
Slavic Pagans and Slavic stuff in general is also something I'm planning for the near future for VIET, in fact (it was originally planned for January, after a Khitan/Chinese-themed update in December, but my sickness conveniently got in the way), so I'll be happy to share ideas and research if you guys need it. As a minor note, concerning Pagania, that's also something I'm intending to add to the 867 start myself, but I can't find any sources on it besides Wikipedia, other than a couple of mentions in some arguably outdated scholarly texts.