I really like how it looks like a colorful little bonsai tree. I agree with what Patrick noted- if you're comfortable with blender/similar 3D software, it might be worth creating a simplified version of the tree using simple primitives (such as UV Spheres for the tree canopy, and using a simple vertex path with a skin modifier for the limbs) along with placing a single light source to help visualize the value change as it turns away from the light source in the tree's canopy. Overall its a really cool design. I do a lot of work in blender/3D art as well as 2D, so I'm looking forward to seeing how this turns out. Let me know if there's anything I can help with.

Hey! Nice work, I love the colors you're using and the twisty gestural limbs! You could try to increase the separation of values to give a more dramatic representation of your lighting. If you desaturate your painting to greyscale you'll see that the you have some room to push things further into dark and light, you have a good start where the image still reads as a tree with separate elements for the trunk and canopy, but it's very subtle. If you pick your lighting angle and accentuate the darker areas opposite the light source you can get some elements to pop a little more. I did a little exaggerated paint over to show you what I mean. Hope this helps! Keep up the good work!!