Was wondering how many total possibilities there are. (If they really wanted to get creative, as you go thru Design Studio they could list how many Model S currently exist in that config. ) Anyway based on Design studio currently, I came up with about 2.7 million but I wasn't careful, so this could be wrong.
Without accounting for the P85D option of carbon fiber spoiler or brake caliper color, I get 2,322,432 If I include those, I get 4,644,864 combinations. I took into account that you can either have the exec rear seats OR child seats, but not both. Also the headliners are linked to the lighting package.