A plain Yugoslav tricolour is not merely a royalist symbol, it is the pan-Slavic flag. 

The plain Yugoslav tricolour flag-map is appropriate for the Yugoslavia-stub template because it is about Yugoslavia as a whole, not just the SFRY. The plain Yugoslav tricolour is not a royalist symbol, it is the same as the pan-Slavic flag and was used by Yugoslavists, it served as the flag of the rump Federal Republic of Yugoslavia and the plain Yugoslav tricolours are seen used today by supporters of a state of Yugoslavia.