This one is actually already in the game, under the anachronistic name "Norse". The Norse people didn't actually have their own religion, but followed the same pan-germanic pagan religion as their southern brethren, they just was the only ones still clinging to it by 867. Sure there were some regional differences in the religious practices between Scandinavia, Continental Germany, and Anglo-Saxon Britain, but non large enough to make it separate religions. Just like how the Celtic Christian practices differed quite a lot from Italian Christian practices at the time, while still being equally Catholic.Or make a Continental Germanic Religion for all Germans and Saxons together.
That is not to say there is no place for additional flavour elements to represent the pan-germanic nature of the "Norse" religion, but right now that isn't first priority, at least not for me...