Not really any features to speak of, aside from the DBS being a feature itself. It did have a hiding place for a sniper rifle in the glovebox. During Bond's wedding, the DBS also featured some pretty flowers.
Trivia:
This was the car in which Bond's wife Tracy is killed by Irma Bunt. and Blofeld only a few minutes after they left their wedding reception. It is generally accepted by Bond fans that Tracy would have lived if the car had been outfitted with bulletproof glass, standard Q-branch issue on MI6 cars.