I recently used a 2 tone HDPE for wall art. It was black on white. The material was 6mm thick. I like this material because it’s easy to cut, relatively quick run time, the finish is clean and because of the 2 tone properties, it really stands out and looks great. As HDPE is plastic, it is also waterproof so can be used for sign making.
My first design was a Jacobite soldier. The design is bought from Etsy, and is an SVG file (Scalable Vector Graphics).