Since I see there has been some work done on transition tiles in the past, I drew up a few potential graphics for Grass-Sand. It would look something like this:
I have the files for all the directions, should they be good enough
Nice Astral, but to use this on the map, everr border-tile must be replaced on the map. I don't think that there will be a GM who will do that much work...
There isn't that much desert sand on the map, but I don't know how the map is set up editor-wise though. I have them, just in case they are wanted in the future.
Also, I have made a forest-grass transition sample using Martin's first mod grass and Shi Long's second forest ground:
A third transition, mining stone to grass. I don't think that this type of transition is suitable for cobblestone, since it doesn't simply fade away. Anyways, here it is:
Once again, it uses Martin's first grass and the normal stone.
