I'd keep them that silvery chrome personally, if I were to paint them a different colour it'd be just the one single colour, gunmetal grey perhaps.
I'd actually be tempted to play with some old chromed hubcaps, smoothie/moons etc:
I think I'd be inclined to go with Matt's idea for the wheels as well, along with Shaun's idea for the body work - open mouth bonnet, smoothed bumpers, and keyless entry (Y)