Powder coating a matte black or grey would be striking on a Model S. The Audi photos in this thread give some indicator as to how it can enhance the look overall. A more extreme example - I was pretty amazed by how the basic Nissan Juke got transformed into the "Juke-R" - they did a lot here but I think they powder coated the wheels with a gun metal grey (matte), the whole thing looks a bit over the top (to say the least) but it does show how you're onto something, powder coating can really add some bite to the overall aesthetic...