This is the back side of with the first step completed. I used a hard pencil to make the deeper lines forming the tree. It is vital that you don't use too much pressure, but gently continue to stretch the metal to the depth that you desire.
This is a closeup of the back with the front having some embossing done on it. You can see that you can easily make textures with the pencils. Knots and bark are achieved by circles and short strokes.
As you work, you can really make the branches lift up and become distinct. See next two photos...
Here is the final shot. I really like how it came out and am excited about trying a different design. It should be a fun project for my students as well!