I really like seeing rpg monsters. Like monsters from the final fantasy series or dark fantasy monsters based off D&D. But environments are also good to see. I prefer pixel art.
the 2d destructive could be done easily. for instance the mana seed collection has a town ruins pack and it matches up with the iconic town set. through eventing you could have it set up to work just like a bomb wall in a zelda game. just do it for each section of the desired structure.
Demand can be very variable. I am also an artist, I wonder what is wanted. However, this is something I cannot understand. So I've left it mostly to my imagination. When I understand this, I plan to work according to demand.