The first step is to paint your canvas (or paper) with you base color. In this case I used green. (no pic.)
In the photo below, I show my metallic olive green paint from Lumiere by Jaquard. I wanted to have a monochromatic background that had some patterning and texture, so I used the green metallic over the plain green base color. Also pictured is my hand-carved pattern stamp. I simply brush a thin layer of the metallic paint and press it onto the canvas. I turn the stamp this way and that to vary the pattern, I reload my stamp with paint after every third press. I have a limited amount of the Lumiere paints available for purchase in my Etsy shop.
Below is the result. Not earth Shattering, I know, but it is a simple yet interesting background technique that will add a bit of interest behind your focal subject. In the finished piece, you can see that I also added the suggestion of foliage by brushing on leaves lightly in a darker green shade, then wiping them off before they dried completely. This recedes them into the background so the bird can "float" in front of them.
The next picture shows the result of pressing my stamp onto a paper towel after I was finished pressing it onto my canvas. I don't know about you, but I think it's cool looking. This will show up in a project at a later date I am sure.