Paladins are getting a huge upgrade with Midnight! The 
Divine Steed Paladin charger mounts for Humans and Blood Elves are being replaced with shiny new HD models.
Human Paladins
For the Human Paladins of the Alliance, casting Divine Steed will summon the blue version of this mount.
Blood Elf Paladins
The Horde Blood Elf Paladins will summon the new red charger mount upon casting Divine Steed.
Other races will, sadly, not be updated. But worry not! Purchasing the 
Glyph of the Trusted Steed from the auction house will replace your racial mount with either a Horde or Alliance Paladin charger.
Relinquished Scarlet Charger
Non-Paladins need not be jealous—the 
Relinquished Scarlet Charger mount will be available in Midnight. This mount is rewarded from the Relinquishing Relics quest.
To see these mounts in action, check out this clip from MrGM:
