Linked here (and also in my Links pane) is a Blog which exists to produce Warhammer Armies "books" written by fans of the game in order to detail some of the regions of the Warhammer World not covered by GW in their official supplements. A supporting Forum can be found here (and in the Links pane).
The books are all completely unofficial, but seem to be of very, very high quality and are freely downloadable.
Covered in the books are such regions as:
and many, many more besides.
If you're looking to try something different I'd highly recommend checking them out.
Please note: you will almost certainly need to "spread out" and include models in your army which are *not* Citadel Miniatures. Also, as the rules are all unofficial, I'd recommend you discuss their use with anyone you intend to game with and also understand that they may well not be permitted for tournament play.