Are you looking for ideas for the roadways or the camper/motorhome pads? High density means a lot of traffic?
You would need good roads for the camper/motorhomes to be able to get to their campsite. Once they are parked they need something substantial for the tires, maybe concrete runners.
For the patio areas, it would be best left as grass.
I am not in favor of campsites that are all concrete and pavement. Many campers like that sort of place.
What is your vision of this High Density Campground? How much do you want to spend?
Currently it's on grass, but we're looking for something more sustainable. Climate: cold and wet winters, mild summers.
How much traffic will you have during the winter?
What do you mean by "sustainable." From an ecology standpoint or an economical one?