NEW MOBS

Red Creeper - This creeper is predominantly red instead of green in color.  When it detects a player it will chase the player until it gets into range and explodes.  However, unlike the green creeper, it will not stop chasing the player regardless of range.  If it gets trapped or is unable to reach the player it explodes.  Bits of lava(non source type) fly from the explosion and land eventually disappearing and setting things on fire until then.

Blue Creeper - This creeper is aquatic only and has tentacles instead of feet.  It is blue in color and difficult to see underwater.  When it comes close to a player, instead of exploding it emits electricity like an electric eel, causing damage.  This does not destroy the creeper and it can continue to pursue the player emitting another electrical burst after it recharges after a time.

Crow - This bird delights in destroying fully grown crops.  If crops are not harvested promptly, crows can come in and eat them instead.  A large swarm can devastate farmland.  A counter to this may be building a scarecrow using an armor stand.