an old portugese favorite is to marinate them in whisky and extra virgin olive oil. sounds odd, but quite nice and the whisky (pref not bourbon - try a malt or scotch) will give a nice seasonal taste. just eat them as a snack, or serve with a salad as an entre.
as they are already cooked, this could be difficult, but a great italian dish is to take the shells off, and make a prawn stock with the shells, heads etc. take the stock and cook the prawns and skinned zuccini (we call em something else so sorry if the spellings wrong) in it. after this, mash up the zuccini and prawn, use as a raviolli filling.