A uAvionix AV-30 or one of the new Garmin 3" instruments wouldn't look out of place in the Monocoupe at all. And would add significant functionality to the aircraft. But I know, purists...
Nice and simple from the 1930's, probably just like Van envisaged for the original RVs!
The iPad/tablet off to the side is surprisingly unobtrusive, and I just love the wood along with the metal fittings.