Interjection: About three years ago I had done a series of tiles of the seven chakras. Each of the seven lotus mandalas is on a white Zentangle tile; I used a color wash, pen and ink, colored pencil, and tiny gems. I've searched the blog, and apparently I didn't post a picture of it back then, so before I continue with the trees, here is Chakras.
I had done two or three trees with metal foil in the background. It struck me that the long format would work well for a series of trees, but horizontal this time. It's 6"x36" and I would need nine tiles, so I did more. Here they are, loose on the table.
All have metal foil; one has holographic strips; one has silver sparkles. I decided to continue with the 'squares' theme around the sides. I alternated various acrylic metallics.
Here is Treeline, finished: