Highlights include:

• Players may now create death knights on any realm once they reach level 55.
  Racial restrictions on mounts have now been lifted. Night elves on mechanostriders? Tauren on raptors? You’re not seeing things.
• Tapping: All player spells which cause a creature to become aggressive to you will now also immediately cause the creature to be tapped.
• All flasks no longer require an alchemy lab to create.
• The Obsidian Sanctum: Players will now be affected by Twilight Residue when they leave the Twilight Realm. Twilight Residue grants immunity to Fire and Shadow damage for a few seconds.
• The Wintergrasp Aura should now properly update in all instances, transferring the buff when the zone control changes.

You can read the full listing here or here.

Customisation will cost $15 and does not include race or class it does however include the characters name. So in effect instead of just changing the name of a character now, you can also change the race and facial features.

More details in the FAQ here.

You can read the full list here.

No real details on how to obtain most of them (yet) however.

You can check them out along with screen shots here.

The list is not complete and is still being updated as more items are found, so check back later.