Moss should be able to expand onto Sand and/or Sandstone.

Moss can grow on sand in certain conditions, and it would be very cool to see mossy deserts, or at least patches of moss in a desert (akin to an oasis). It would also make terraformation/rewilding projects possible in Minecraft. If for example there is a water source nearby, as well as darker illumination than the maximum, moss should be able to expand onto sand-like surfaces as that would match its' natural growth.