I have been etching Sterling silver for several years now to make unique textures. For etching base metal plates, you can use nitric acid or ferric chloride (which is a bit kinder, but slower) and get very detailed results. There are several ways of creating a resist of your design but the easiest is to use PnP which is a blue film that is used for etching copper circuit board. You need a crisp black and white design and a laser printer, not inkjet, as the toner acts as the resist. The design is then transferred with care to the metal using heat and pressure - I use an old iron. If you are not keen on using acid, you can electro-etch.
The results are lovely detailed plates of any crisp black and white design you choose. There are resources on the internet that will give you detailed instructions of these methods.
Good luck!