I agree with Erny...not a whole lot of restrictive background to be trapped by but enough of a framework to hang a story on....which is just the way I like it.
I'm personally very much interested in the idea of ex-pat dwarfs living in the empire...Erny can you give me some sources from WFRP that would be useful in this regard?
My entire image for my dwarf collection is of a prosperous city on the fringes of the Empire that has a very heavy interest in mining and has therefore attracted a large number of expat dwarfs. Thus my dwarf army is based around the Marauder Puff and Slash dwarfs (and now WK dwarfs) which represent the City dwarfs that have adopted Empire military technology and Dress (Pike dwarfs, Dwarf "Knights", etc.) as well as use the more traditionally attired dwarf units to represent the dwarfs from the outlying towns and mining communities (Bugman's, Prince Ulthers etc.)
On the subject of Chaos dwarfs...I really like the way that CDs were represented in 3rd ed (and earlier) they were more like mini Chaos Warriors...with similar armor and weapons...and none of that big hatted bull god loving non-sense of later years. The core of my opp for for my dwarf/empire army is a large warband of Chaos dwarf slavers and their Green Skin minions.
Cheers,
Blue