Whilst clearing out my garage I found a box of vinyl floor tiles with a small mosaic pattern. Rather than throw them out I experimented with making some dungeon/crypt tiles.
The vinyl is 2.5mm think and is easily cut, just a few score lines on the top surface to cut through the top printed layer and they snap nice and cleanly.
I just cut them to shape then applied a household matt varnish before sprinkling a mix of sand/dirt and green flock, the latter being added to the areas between the slabs to look like moss. Once dry I sealed them with a second coat of the same varnish.
I've used 4 tiles from the box of 20 and have enough to cover a 4' x 4' table, total time involved in making them around 3 hours (excluding drying time)