The only styling bits I've seen have around the UK have been grills, front lips and different exhausts. There are also a cple of options for the rear lights like swapping the rear red fog for a clear one so the rear matches.
Apart from wheels, lowering the ride height, front lips and lights there's not much stuff for the hatch in the UK, you'd have to look at the US, Oz or Japan to get aftermarket styling bits.
http://www.just-subaru.com/
http://www.japanparts.com/
http://www.avojdm.com/
http://prorracing.co.uk/
http://www.scoobyparts.com/
http://www.scoobyworld.co.uk/catalog/index.php