Best cosmetic changes for Porsche Cayman?

Quite possibly the most beautiful Porsche currently made, your Cayman doesn't need the added flounces. Personally, I recommend against it. Attracting attention to the car, if you park it in public, can bring the wrong kind of response. Don't make it a target of jealous people. I understand the desire to add little personal touches; do it with things like colored wheel center caps, Porsche crest valve stem covers, custom floor mats, etc.- very small details visible when the car is examined closely.