If you have used the <flag> tag you should provide the flag files. They have to be in PNG format and better if they are 300x200 pixels and you provide a SVG file for it. To obtain SVG flags of almost all countries in the world and some other divisions, you can consult the Sodipodi flags collection.

As noted previously, we encourage you to provide blurred flag files for flags that have the division written on them. The same requirements apply to the blurred flag files as to the regular flag files. While there is no prescribed naming notation for the blurred files, we recommend saving these down with the name of the original flag prefixed with blurred_, e.g. “blurred_albania.png”