As long as the actor doesn't have any easily-identifiable characteristics that will cause an audience to question their validity for the role, then who the elf cares?
I saw The Inheritance in London and didn't know any of the three young male leads and assumed they were all gay. Apparently not, but they were all wonderful.
The one actor who seemed ill-cast was Vanessa Redgrave as an American earth mother. Ms Redgrave- like most British actors of her generation- struggles with an American accent and because nobody else in the production had had similar difficulty, she stood out. (My first thought when she began talking was, "I wish I could see Lois Smith in this part!")