Roger, careful with the floor it seems much lighter in color than the walls.  can not tell from the pics if the floor was the same material as the walls.  If it is and it is that light I would think there is quite a bit of spalling in the stone and that would not surprise me with serpentine.  If this is the case do not resurface the floor just clean and polish it to best possible but let the customer know that you can not remove all of the damage on the floor. 

Dark verde stone is very easy to hone and polish.  It's the light mint colors that do not polish well but that just the nature of the stone.  Note serpentine is not a great choice for showers since they are very susceptible to moisture and will warp/curl or spall when saturated that is why they should be set with epoxy or atleast speed set

since basic setting materials may cause problems.