Grand Alliance: Order

Aligned as one, the civilised races of the Realms go forth to claim the lands and restore Order, Sigmar's Sigmarines Stormcast Eternals leading the fray.

Armies of the Aelves

Look! It's the Elves Aelves! As fancy and effeminate as ever, and now split into 11 (!) different factions.

Darkling Covens -

Daughters of Kaine -

Eldritch Council -

Lion Rangers -

Order Draconis -

Order Serpentis -

Phoenix Temple -

Scourge Privateers -

Shadowblades -

Swifthawk Agents -

Wanderers -

Armies of the Duardin

The Dwarfs Duardin are back, and are as grumpy and beardy as ever.

Dispossessed - Classic dorfs.

Fyreslayers - Expanding on the Slayers, here's a whole faction of them (and no, they don't slay fire, incorrectly spelled or otherwise). Ride atop giant salamanders and possess very little in the way of clothing.

Steamhead Duardin - Steampunk dorfs.

Armies of Man

Now relegated to "silly normals" status, mankind are now the Imperial Guard to the Stormcast's Space Marines.

Collegiate Arcane - Assorted wizards and magical scenery. You can now play a full army of dress-wearing spellslingers! Rejoice!

Free Peoples - What remains of the Empire list. It turns out that thousands of years later, in a totally different place in time and space, men and women still dress in exactly the same silly feathered hats and pantaloons and there has been no cultural shift or development in that time whatsoever. This is despite the fact that the denizens of the Realms are generally described as being barbarians (which the Stormcast have been drawn from) and all other vestiges of human society have been laid into by Chaos hordes.

Seraphon

The lizards are back, but they are now demon space lizards, apparently. Very blue and very angry at Chaos, they appear from nowhere to mulch the gribblies at every opportunity. Due to racial memory, the Skaven are absolutely terrified of them.

Stormcast Eternals

Extremis Chamber -

Stormcast Eternals -

Others

Ironweld Arsenal - A bunch of Human and Duardin engineers came together and compared notes. Cannons and general siege machines. Seems to be intended for use as an ally for artillery support, but does also have things like gyrocopters included too.

Bretonnia (Warscroll Compendium: Bretonnia[1]) - Not a faction in the fluff, as its models are now discontinued and they've gone the way of the dodo. Still have rules on the GW website, meaning you can use them to have your own flavours of knightly orders and stinking peasantry.

Pantheon

Sigmar -