I voted for Charlemagne, though they were all tempting, the Song of Roland is one my favorite medieval legends, in itself and in various re-imaginginings I've read. It's also been sorely overlooked as a setting for most dark/ages medieval games also, generally passed over for King Arthur remakes or later periods like the crusades. Looks like it'll be viking though now that I've seen the results though;), My suggestion there would be maybe to aim at the viking/norman invasions, Have Saxon, Viking and Norman fighting it out to control britain. Could be fun.