Not sure exactly what style you're thinking of, and don't know of any links to patterns.
But, I made a new bracket for my tag and turn signals and a few other things. Mostly from old street sign stock. I come up with a mental image of what I want to fabricate and use file folders or paper plates for stock to make templates. If you are working with sheet metal, sheet cardboard helps work out the fabrication issues as you cut and bend and tape it into shape. Paper plates or folders are a good thickness to work with for templates.