I'll give it a shot...
Arabia - The crescent and star are symbols of Islam, the de facto regional religion of Arabia.
I simply did a Google search (followed by an image search) using "_______ national symbol" or "______ cultural symbol" and found most of them fairly easy...
Arabia: Star & Crescent (Symbol of Islam)
Well google search is useful in terms of reflecting what is in popular culture but in deeper research we see different results.
You actually faced one of the most general misconceptions about Islamic culture and Arabian culture. What we know as "Islamic" now is the result of combined cultural elements from Turkic, Persian and Arabic traditions. Arguably, Arabian impact survived only in language and alphabet today whereas other elements come from mostly peripheral cultures.
In insignia case, the crescent, star and other celestial elements are definitely derived from Turkic culture. One of the main characteristics of Turkic steppe/nomad life was sky cult and entire ritual and belief system was based on it. One can observe this in every single Turkic culture all over the Eurasia thus
the Ottomans' insignia is
three crescent. Actually they never used it like family crest or imperial flag but all of the military signs contains either
crescent or
eight-point star which is the oldest insignia in steppe culture.
With the domination of Turks over the Islamic world at 12th century, Islam started to represent a new cultural style and therefore in Anatolia a new kind of syncretic Islamic belief emerged (Sufism and shamanic practices) by the impact of dervishes from Turkestan. That is to say, what we know "Islamic" today can originally be element of Turkish culture.
Especially In Europe, Image of Islam depends on two cultures: Andalusian/Umayyad and Ottoman/Turkish culture since they had the closest relationship with European continent. But obviously Ottoman impact is more recent and still determines the orientalist imaginations of people about Islam.
I know this information does not effect game experience too much but since op wants to reveal insignia facts, I write this to change general misunderstanding.
Ottomans: Variation of the Star & Crescent (Specifically symbol of the Ottoman Caliphate, 1844–1923)
Ottoman royal family dates back to 13th century and their descendants still alive as Osmanoğlu (Son of Osman).
But Ottoman Caliphate started at 16th century by the Ottoman conquest of Egypt and the decline of Mameluke dynasty.
Sultan Selim I (Yavuz) was the first Ottoman caliphate. On March 3, 1924, first president of Turkish Republic,
Mustafa Kemal Atatürk abolished the institution and that was the end of Caliphate.
