Shinnok's Probably Based On The Fallen Elder God Tongtian Jiaozhu
Shinnok's backstory as a fallen Elder God may not only be inspired by Mara the god of sin and lust in Buddhism. I also thought one of character that may have also inspired the fallen Elder God's character.
The fallen Elder God Tongtian Jiaozhu whose name is translated as Heavenly Grandmaster. He's the younger brother of two Elder Gods namely Yuanshi Tianzun and Taishang Laojun. The fallen Elder God has been depicted as a prevalent antagonist in many legends and classic novels as well as some Wuxia series on TV. He's also the head of the Jie sect - the possible inspiration behind the Brotherhood of the Shadow.
While Shinnok may be more or less a Chinese version of the rogue Asgardian Loki but one can't deny Mortal Kombat seems to dwell on Chinese mythology. This is just my speculation but what do you think?