By now, you know to expect a lovely artbook and/or soundtrack as a pre-order bonus with any new Atlus game. That's just what Atlus wants you to think, and then it shocks you with a Vita skin! Surprise!
The "limited" pre-order bonus for Persona 4 Golden is the above Vita skin, along with eight Persona 4 Golden Vita wallpapers that line up nicely with said protective skin. The game (and the skin) are due this fall.