This looks so much like our dry creek bed with our little apple tree in the middle. Maybe adding large rocks around the other side of the tree will make it feel more balanced. Also, I like the itty bitty rocks along the outside of the larger rocks.
Not only is the addition of lighting an important safety feature, but it lends a lovely esthetic to the evening enjoyment of this garden/yard. Design by Rick Barrett, Construction by Maverick Pickering.