u/Tibot_beep_boop

This is more about looks since the May Queen in folklore is known for being a symbol of purity and respect for the earth, which Varang does not represent in avatar. But with the white face paint with a painted red (it can be any colour in the Gaelic celebration) and the headdress it feels they look very similar.
Also in Gaelic culture fire festivals are used as a celebration for purity because it believes that fire brings/is purity. Varang claiming that fire is the only pure thing in the world and the ash clan holding fire festivals in the movie.
Though it could just be a coincidence and has no inspiration for Gaelic culture at all.