A floor is a colour map with a normal and a roughness beside it. Heimdall3D reads all three when the colour map is first seen, so the surface arrives with its own relief and its own shine instead of a flat picture of one.
Download one: sand.zip · snow.zip · asphalt.zip · gravel.zip · terrazzo.zip · brick.zip · cobblestone.zip · slate.zip · hextile.zip · checkerplate.zip · leaves.zip · rubber.zip
Each zip holds three maps at 1024 x 1024 and a credit line. Unzip all three into %APPDATA%\Heimdall3D\floors together: the companions are read when the colour map is first seen, and a floor already prepared is not prepared again. Add on the Floor card opens that folder.
Every one is CC0 and tiles without a join showing. Ten are by Lennart Demes at ambientCG, brick and slate are by Dimitrios Savva at Poly Haven, and each zip names its own author and source.