The network dialog (and possibly the lobby list) should be able to display country flags in the OList (#3787).
But creating an XML file with 250+ times the same icon definition seems not only tedious to create but also tedious to maintain (imagine wanting to change the icon size for all flags, removing removed
flags, adding new flags).
Since there are only two properties per icon, there seems to be hardly a reason to require XML files defining them; other than maybe a consistency argument.
A second use case would be loading resource icons dynamically, so that mods don't have to overwrite the setup_resources.xml file. That would also allow combining mods that both change resources (if that makes any sense).
With Engine.TextureExists one can test that whether a png file exists (even if it only exists as a dds file in the archive).
Depends on D1701.