Thinking if you have the cardback equipped you could have a different hero power.
Warlock: 1 mana: Create a random demon card in your hand. A random demon is worth quite a bit less than one card from your deck, so I costed it a lot less. Good for demon and handlock strategies.
Hunter: 2 mana: Create a random Hunter secret in your hand. Hunter secrets are generally good. Good for secret based strategies and more controlly Hunter decks. I think if you ever want a viable control hunter this would be a good first step.
Priest: Passive: Start with 40 health. Gives you more breathing room vs. Aggro. Great in Wild with Reno. Or future full heals.
Demon Hunter: 3 mana: Summon a 3/1 Illidari with rush. Makes Pally cry. Good control option with enough attack to be a threat.
Pally: 2 mana: Create a random 0 cost paly secret in your hand. Good for secret stragegies. A ton more interesting than a 1/1.
Shaman: 2 mana: Create a random spell with 'damage' in the text. It costs (3). Super bursty and random. Sound like anyone you know?
Rogue: Passive: Your minions have stealth the turn they are played. (not summoned) Seems super flavorful. Maybe quite powerful.
Druid: Passive: You start the game with a copy of Wild Growth in your hand. Makes ramp strategies much more reliable.
Warrior: 2 mana: Deal 1 damage to a friendly minion and give it rush. Some enrage/frenzy support.
Mage: 2 mana: Your hand size increases by (1). (you don't draw) Great for combo/control options.