All sand games are equally gritty. Personally, I like building sand castles on the beach, but then I cry when the waves knock them over. Stupid waves.
Thinking a little more macroscopically (but hopefully OnT): How about if we could determine the overall shape of the entire *world*?
Possibilities:
Flatworld=An infinite plane that spreads in all directions. If you somehow reach the edge of a given map, a new map generates itself, ad infinium (or atleast ad-your-computer's-limits). This world might only be 15 Z levels thick, meaning when you dig through the last one, you come out the other side, to another (different) infinite plane. Magma is rare.
As an alternative: Metaphysical Vanceian Flatworld=as above, but dig down deep enough, and you might find an entrance to the Underworld, home of the undead, demons, monsters, what have you. Climb high enough, and you might find a way into the Overworld, home of angelic beings. Dwarfs and other creatures who die on the middle plane, resurrect in either the Underworld or Overworld, and can even possibly find their way back to the land of the living.
HollowWorld=Standard Wellsian vision, dig 15 Z levels down, and find yourself in an entirely new, traditionally prehistoric (with a twist) environment.
Magma, again, is rare, and demons rule the savage lands.
RealEarthWorld=The spherical Earth-type standard. Magma is everywhere, if you dig down deep enough, and new Z levels are generated after 15. Walk, or sail, over enough maps, in one direction, and come back around to where you started.
TreeWorld=Norse Myth personified. Everything exists in several different small worlds (1 map wide, each), which are interconnected by an enormous World Tree. The World Tree (aka Yggdrasl) is mineable, but beware the giant insects, and even bigger animals, living on, or in, it.
Budong-World=An alternative Norseish version of the world, where the Earth is just a titanic corpse (or living body) of some ubergodly creature, floating in space. Mineable and finite, magma exists as the world-being's bloodstream. Bone can be mined. Dwarfs and other creatures are just what amounts to parasites, viruses, bacteria, fungi. Watch out for the immune system!