Ah, I started a similar example/explanation as Reo yesterday, although I'm for the dither in more ordered form!
ignore the dupes:
Silhouette: it might be a mushroom or something at first glance, you don't have colour info to help so this is even more important to disambiguate. The trunk is pretty huge for the canopy and there's little sense of it being an open mass of leaves; looks quite smooth as yet.
Only two values to play with so you could really do with leveraging the whole range available ie. areas of full black to full white; atm you're treating things more like a line drawing.
I think something pretty high constrast, akin to brush & ink is a good way to think here; flat black stencil shadows, and to push back stuff on overlap for clarity, directional halftone/texture around form.