I know I've been posting a lot, but I had this thought about Iceland. I've never been satisfied with the way it's portrayed in the game (vanilla too), since it was uninhabited in 769. However, provinces have to be owned by somebody in this game.
Well, one thing that's occurred to me is the possibility of it starting with one Irish Catholic Bishopric (representing the Papar) in 769, and three empty provinces. A single Bishopric with no buildings would almost be like a wasteland, but it would be more historical than having the Norse inhabit the land. Since the empty provinces weren't conquered from a nomad, my understanding is that they'll remain controlled by the Bishop regardless of him dying. If the island does become conquered by an outsider, there could possibly be some sort of event that flips the culture and religion and replaces the Temple with a Tribe, with more events to add Tribes to the other three provinces. Portraying Norse colonization as a conquest of the Papar isn't accurate, but it seems more accurate than having them just exist from the start. Even better if there's a way for an Adventurer to seize the lands; then, you'd have an independent Iceland that should end up fracturing due to Gavelkind (which is kind of like the Icelandic Commonwealth).
Alternatively, there could be a special "Wilderness" nomadic character that, like Muhammad, has no portrait and is, through various traits, basically made into a non-character. No army, no taxes, no ability to interact. You "colonize" land by conquering it from the Wilderness (which really just means squatting on it for long enough to get your War Score up), and then building whatever Holding you need to secure it. If the Wilderness ever somehow gets land, it should destroy all of the Holdings present. On the map, I'd think this would only be used for Iceland, but a modder interested in Norse colonization could extend this to Greenland and Vinland.