The secret is to ensure each gap in between the trees is visually different from the others. Not one tree shape is repeated.

The waterfall in the photo is a visually implied rectangle. The two sides are not visually different. The silhouette shows a correction.

The mountain peak in the photo is too close to a triangle and the protrusions on both sides are cloned. The silhouette is an improvement.

Even though the shape of the tree in the photo is not scientifically symmetrical, from an artistic standpoint it is implied to be symmetrical. The black tree silhouette is quite different on both sides and its contour is very interesting. The artistic version resembles the tree in the photo. It is not a copy.

The photo is displaying a rare case in which the rocks are abstract by themselves and needed very little tweaking. The silhouette was done almost to face value. Sometimes nature will cooperate with you. (This photo got added to my pictionary.)

The parallel sides are gone. The cylindrical shape is no longer present. The smaller branches are different from each other. This artistically designed tree trunk shape by far is better looking than what we see on that front lawn.