No, but I have been to beaches. No grass on beaches here. Not saying it is the same everywhere else, but it seems... Weird to me. I dunno if it would fit. But, I'll think about it.
My idea is kinda similar to the desert - adding a new sand tile that Wild Pokemon appear on. perfect for crabs, oysters, birds and fish.
Volcano tiles do kinda exist already in Ruby, in Mt. Chimney, but I'm hoping to expand the amount of volcano tiles.