On dead races you could talk about the Ikarrans (sp?), Dilgar, Markab and the Builders of the Great Machine. The Orieni stuff I find interesting as I think they are such a great race to see and hope Mongoose perhaps publish some stuff on them in the near future.
Was also going to say if there was the possibility of a book which talks about: Tak'cha, Soulhunters and Strieb but i think that is derailing the topic of this post so will save that for another time.