Just a few civs and info I would like to see in civ v xps:
Vikings, Ivar the Boneless, Berserkers and/or longships
Celts, Vercingetorix, Gaellic Warriors and/or Brithish Charioteers
Maori, Rawiri, Cannibals
and then of course Carthage, Mongols, Huns, Franks, Holy Rome, and even Romano...