@asheera gave us some good examples of faces that could be a good basis for the art team. There is another thread on that topic that veered off into making connections between elves and the peoples of the earth and that thread got abandoned. Better to revive that thread than remake it here. Elven features are angular, delicate and unlike any one human group. The art in the Tome of Foes does a good job -- I especially like the drow in the pink dress. She just isn't from this planet, is she?
In addition to the elf heads we have now we need some that look otherworldly.