This is why I made this little gift for you, really look at it, and you can see and emulate what I've done. It's not magic, it's just examining how the tiles work together. I suggest placing the areas of the canopy with transparent areas on layer 3, the solid dark green canopy filler on two, then wherever the dark green is, you can cover it with another layer of canopy on layer three. Even just small patches of that make it more interesting.
Place your trunks on layer two, and don't forget to use the alternate versions at times (the ones with underbrush). On layer three you can overlap some extra small plants, trees and vines.