I highly doubt that the playable characters will even have faces. Much like the aliens from Mass Effect the name escapes me, Tali was one of them, and of course Master Chief the big kahuna himself, never seen his face (until 343 made Halo 4 and you get to see Steve Downes eyes in CGI). So, to answer your question, I don't think they will look like anything other than armored up humanoids, and seeing as to how The Traveler is hovering over Earth, all playable characters will be human. Also, not being able to see their faces or skin would allow you to pretend that you aren't human, if you so wish.