As much as I'd love to be involved with this excellent debate about whether trees do or do not grow out of rocks, I think, Matt, that you need more color. Too many natural colors. Try some flowers and maybe even jungle-type plants to vary it up a little. Trees are great too, and little patches of "gardens" with trees and flowers will help make the pathway a little less dull.
Anyway, I like the structure of the coasters, especially thewater ride. Don't be afraid to experiment!! Hope to see updates soon.