I found a solution to a relatively common problem. When you try to use an image hosted on the Particracy Wikia, the game does not recognize the file resulting in a "broken" flag.
The solution to this is to modify the URL. When you click on an image on the wikia to copy the URL, you need to replace the word "static" with "vignette".
This is also relevant for posting on this forum.
E.g. if I tried to set https:// static . wikia. nocookie .net /particracy/ images/b/b4/A_new_more_Esperanto-looking_Zardic_flag.png/revision/latest?cb=20230912145900 as the flag of Zardugal it would not work (added spaces to this does no become a link)
I changed the URL to https:// vignette .wikia.nocookie .net /particracy/ images/b/b4/A_new_more_Esperanto-looking_Zardic_flag.png/revision/latest?cb=20230912145900 and now it works.