We have concrete now which is pretty versatile but making the entire map out of it makes the appearance dull.
I recommend four more materials for building.
-Grass: Slab, Ramp and Wedge. Grass could do a great job designing surroundings.
-Dirt: Slab, Ramp and Wedge. Could be used for custom dirt tracks.
-Steel: All possible variants. Could be used for designing structures like bridges, railway crossings, containers, cranes, etc.
-Asphalt: Slab, Ramp and Wedge. Similar to concrete but in diferent variable colors to fit the base map's roads.
They could have different physics like driving on Steel is difficult because it's slippery, Grass releases Grass particles under your wheels, Dirt does the same with dust.
Steel could have different color variants as well, one of them could be rust