Describe the solution you'd like
As a grave ages in a given biome its texture (and possibly model) should begin to be "taken over" by the elements.

For example, in the ocean it could begin to deteriorate and become covered in kelp (and/or barnacles for coral reefs), or become covered in grass and poppies/dandelions in the plains biome, or even begin to become "covered" in sand in the desert.

I'll eventually need to find someone to help with these textures/models so feel free to leave a comment if you would like to help! In addition, suggestions for each biome are more than welcome as well! :)