This kind of reminds me of plants that appear in the Dr. Seuss books. ^^ Very well done (even though, I know, this picture was done over two years ago). ;3
Oh yeaaaah ! I have similar ideas of giant mushroomish vegetations but you are far more developed than me in achieving that sort of rendering. I love it ! I still floundering with my whishes with the subject so I'm really envious. You're pics are great ! I hope you'll do more mushroom landscapes !
Late answer sorry!, but its just a photoshop standard chalk brush set to opacity/flow on pen pressure, its like the round brush but more of a angular shape, I used a different for the far away mushroom things, just a custom one, wasnt really required