This Sketch file includes several International road signs. If you're interested in the design history of signs, we suggest you look up Margaret Vivienne Calvert - a British typographer and graphic designer who, with colleague Jock Kinneir, designed many of the road signs used throughout the United Kingdom, as well as the Transport font used on road signs, the Rail Alphabet font used on the British railway system.
Furthermore, take a look at Wikimedia's library of SVG and vector versions of road signs in the United States. It would be awesome if someone takes the initiative to organize, properly name, and share all of these signs in a Sketch document ;). Send us a note if you're the one.