I always liked Albion in the game. I'm still trying to get a Truthsayer model for my army, but every time I see one on ebay it costs and arm and a leg.
More fluff the merrier! The bird riders angle is interesting. It doesn't fit with the more traditional marsh dwellers we saw during the Albion Campaign or the Gotrex and Felix book, but it would be neat to have a more diverse group of tribes. Just like early real world Albion. Some in the highlands, forest, moors, marsh, etc.