I'd also like to mention something else, going back to Dave's comments on the Viking setting game he's playing. In Old Norse, viking isn't a noun, and it's certainly not a demonym or ethnonym. It's a verb, and it translates roughly to "raiding". In other words, when Norsemen said, "blah blah viking...", they were saying, "blah blah raiding...". Viking is something you went and did, and "a Viking" was a person who went and did that thing. You might say to your friend, "Oh, so I went viking recently, and look at all this shiny gold I got from those dumb Christian monks who keep all their shiny gold in undefended churches devoted to their silly (and, apparently, powerless and inferior) foreign god!"
The reason I'm pointing this out is that, for most of the Viking Age, actual vikings were effectively small-ish bands of pirates and raiders from a culture where such behavior was acceptable, especially if done to outsiders, rather than something that was done in a top-down fashion on the orders of a central authority. Well, mostly. The Viking Age actually coincided with a population boom in Scandinavia which was beginning to allow for more advanced forms of social organization, and was part of a complex process that would eventually see the foundation of the modern Scandinavian kingdoms of Denmark, Norway, and Sweden. Eventually, Scandinavian kings WOULD build their power to a greater or lesser extent upon organized invasions, such as the Danish/Norwegian conquest of large portions of England, Scotland, and Ireland, or Rollo's siege of the Īle de Paris, and subsequent receipt of a large ransom and control of the region of Normandy as an official vassal of the French king in return for stopping all this troublesome plundering and raiding, but this largely happened right towards the end of the Viking Age, and the Scandinavian kings pretty much gave up on going viking after the death of the last real Viking king, Harald Hardrada, after his failed attempt to reassert Norwegian rights to the English throne in 1066.
The truth is, the vikings just liked shiny things, and the Christian kingdoms of Northern Europe at the time had lots of juicy, poorly defended targets just lying around, because Christians hadn't been making a habit of pillaging churches and monasteries, so they started taking stuff. Then, as they saw how poorly prepared their victims were to defend against small bands of seaborne raiders, as opposed to proper armies, they got bolder and bolder until they got beaten, conquered places, or were approached for negotiations. Because they were a lot like other Germanic peoples of the time (including the Anglo-Saxons and the Franks), in behavior if not necessarily in religion and culture, and they really just wanted to improve their own material conditions. They just happened to be really good seafarers, and Northern European defenses were geared toward addressing threats from other European land powers (obviously, the British Isles were a bit different, but still).
Actually, while they did love fighting, and the ideal of dying gloriously in battle was a big part of their religion and culture, what they REALLY loved was trading with people, and that's what they mostly did as they became more organized and better acquainted with their neighbors.
So, I guess what I'm saying is... if you guys want to form your own band of vikings and do whatever makes you feel good, whether that means raiding villages on your own terms instead of under the orders of a king too ruthless for your tastes, or having one of them, as their leader, straight up just challenge him for control, then that would be perfectly acceptable behavior on the characters' parts. Though, if they went so far as to challenge their king, their leader's loss would certainly result, at least historically, in him (if not all of them) being made to suffer horribly as an example of what happens to failed usurpers (assuming he lived through the failed challenge in the first place), and if they won they might still have ruffled a lot of their new followers' feathers by doing so in such a manner, which could mean anything from breaking up the raiding party into multiple disassociated groups all the way to outright denial of authority and attack by the men (if they were fond enough of the defeated king/disdainful enough of the usurper, if they just didn't think the usurper could lead them to as much wealth and glory as their more ruthless predecessor, or if they felt their standing and authority under the new ruler would be reduced in favor of new lieutenants, such as the other party members). Either way, though, you have plenty of options in a Viking setting (and if it's actually a NORSE setting, rather than a specifically Viking setting, then even more so), and I think that you guys should be able to find ways to deal with those problems in an historically believable way.
Hell, Harald Hardrada's story is pretty telling: he spent years of his adolescence and early manhood in exile in Kievan Rus' under the protection, and in the service of, Yaroslav the Wise; then moved to Constantinople, became the commander of the Varangian Guard, fought a ton for the Byzantines, and made a fortune in the process; and finally went home and regained the throne of Norway, and spent the rest of his life centralizing the administration of Norway, minting coins, and trying to conquer Denmark, and failing that, England. Also, just a note about Harald, his death at Stamford Bridge in 1066 is considered the end of the Viking Age, and just to show how much things had changed some three hundred-odd years after the beginning of that era, Harald was a Christian; his twenty-year reign was one of peace, stability, and prosperity for Norway; and most of his raiding was of Denmark, as part of his attempts to gain the Danish throne, rather than of somewhere outside of Scandinavia.
Anyway, I don't know that any of this will actually be helpful (or new information) to you, Dave, or even still relevant this long after your initial comment, but I enjoyed talking about one of my favorite historical periods (and as a history major, among other subjects, that means something

), and maybe you'll find something useful in my ramblings on the topic of Vikings.
As a separate note, I'd be really interested in any thoughts you have on all of the other things Drul and I have discussed here, if you get the time and happen to have anything to say on the subject.
