Choose a pair of sunglasses that keep the colours true (red and green are the most important). A good lens should give decent UV protection and glare reduction. When you're wearing them you will notice a marked improvement when viewing clouds in bright, hazy conditions. I use Raybans, there is a range to choose from.
Thin arms useful under headset. As mentioned already, don't go for Polarised, they will obscure instrumentation when viewed at the wrong angle.
As for shoes, wear whatever fits your feet comfortably. No prizes for stylishness, it doesn't matter.