I would like to add a couple more ideas to the tutorial described in my previous two posts (below).
As you can see, in this tutorial I explained how to use a lever paper punch to create a custom stencil for embossed design. However, you may also use commercially-available stencils. Please refer to the picture below. To obtain this design, I used two plastic stencils - one of them is for a letter and the second one is for a decorative corner.
Please note that a better (deeper) design may be obtained when a thicker stencil is used. The design created with a thin stencil is more shallow and less visible.
Here is another idea: to create your own pattern, cut a stencil out of a thick paper.
I decided to make a rather complicated stencil, with two trees (see below). After sketching the trees, I cut them out with an X-acto knife. I can now use the obtained silhouettes of the trees to make an impression in my clay in the shape of these trees. However, if I want to have these trees embossed in polymer clay, I will have to collect all the little cutouts of the spaces between the tree branches and glue them onto a separate piece of paper.
Too bad I cannot show you this design finished in polymer clay since I am still away from my studio... You will have to use your imagination and experiment a little bit to use this approach.