Oh I didn't thought at that. Freeciv's software only uses PNG flags for any purpose, all around, everywhere. But, new flags which are added to Freeciv must be SVG. All the flags are present in both formats. SVG is how flags enter into Freeciv, but then PNG is how they are actually used by the game. That's because all the flags are manually cut in the required sizes during any release process, with the aid of a script. That's it, from the original SVG images, smaller icon-size flags are obtained, such as the small unit's shield flag, the medium nation-selection flag, and even flags shown in Greatturn website come from the very same SVGs included in Freeciv. That's it, SVG is the master file from which all the rest is derived.