I tried to capture the updated (2014) standard back / rear seats in the Model S for you.
The ergonomics of the seats changed completely. While I wasn't able to sit upright in the old seats without touching the roof it is now easily possible (6ft / 182cm). I was also able to rest my head on the new higher head rests which are a little softer too. This Model S was equipped with pano sunroof, so it might be a little less headroom in non pano versions.

I still have to try the new generation premium seats (front & back) which have already reached the first customers which ordered the P85D. I will report about the asap.

Thanks for watching!

Yours truly

M