Hey Mech!
Those are some really nice suggestions.
I have a few concerns with creating societies: firstly, often devotion to specific gods (in the sagas) tends to be a personal matter rather than something like a cult. At least from what I've read (e.g. Hrafnkell freysgoði); at a stretch perhaps it takes the form of a very small, close knit fellowship of friends or blood-brothers. Secondly, I'm a bit torn when it comes to strengthening stereotypical portrayal of Norse religion, so it needs to be subtle and well documented (refer to my first concern; I doubt we can find proof of any significant pan-Norse societies).
Yeah, the cults I am talking about are not well-attested in the Sagas, or when they are it is often accidental. That being due to the Christians who wrote the Sagas not being interested in how the pagan religion was practiced or organized.
However in writings that pre-date the Sagas about or related to Norse Society and other older Germanic Societies there is evidence for organizations which could be described as a mix of Cult, Mannderbunds and Comitatus.
For instance in Tacitus'
Germania he describes ritualistic sacrifices to a goddess via drowning. He also discusses a people known as the Harii who paint themselves in black and do night raids, which is theorized to be a ritual society of young male warriors within other tribes potentially dedicated to Odin.
This is an idea that as been attached to the wolf-warriors of Odin, related to a theory Tolkein wrote about, that at the time of the Viking age a "Odinic Death Cult" had arisen and supplanted an earlier fertility-based cult.
The Fertility of Cult at Heorot is a theory pieced together from studying the Beowulf/Kraki story. I am not sure where it stands with recent scholarship but at minimum it was endorsed by Tolkien.
From mostly Roman-Germanic sources, as outlined in Herwig Wolfram's
The Roman Empire and Its Germanic Peoples, we find Early Germanic pagans with religions still recogonizable as Germanic, belonging to ritualized and fictionalized communities of decent with a King acting as High Priest. These communities of descent also act as religious cults and the descent is generally seen as belonging to a God, Monster, or Hero. In any case it makes the veneration of a god not a personal matter, but a family/clan/tribal one.
Adam of Bremen wrote about the Nine animal Sacrifices including humans that occurred every Nine years at the Temple of Uppsala. It was not an eye-witness account, instead he was told of it from someone else, however details about the pagan statues and some of the rites align with other information about the germanic pagan religion.
Odin's hanging ritual is also given credence in Gautrek's Saga where he demands Starkaðr sacrifice his king by hanging.
A recent archaeological dig-site has given some level of credence to the idea of
Shield-Maidens. Not exactly a slam dunk, but its more then we had previously, not to mention CK2 already lets women be Shield-Maidens.
Focusing on the Beowulf/Bjarki angle and the phrase 'Berserk', a case can also, and has been, made for there being a bear-cult not that dissimilar from the wolf cult, but with some obvious.. difference.
As always when dealing with the religion of the Germanic people we are forced to deal with scraps. But, the scraps do exist and while I would not advocate going too fantastical, I think you'll probably find better sources for most of my suggestions than most others. And, ya know, it's a game. =)
