So I got this request as well:
So I imagined that there might be a Tolstoian Christian-Anarchist revolution in the Kingdom of Serbia. It's pretty ASB, but hey, why not.
As to the flag, it's pretty self-explanatory. The revolutionaries kept the old red-blue-white color combination, but removed all royal symbols. The Serbian cross that stands for Christianity is white instead of gold to symbolize both pacifism and a clean break with the corrupt Serbian Orthodox Church to return to the purity of proto-Christianity. The plow symbolizes agriculture, self-sufficiency and vegetarianism.