The Eileen Head is simply Eileen Galvin's head, but her skin is scarred and her eyes are bloodshot. Her eyes twitch erratically and follow Henry around the room, ignoring Eileen.
Eileen makes no comment on it, giving the possibility that the head is invisible to her (in the same level, it is revealed Eileen can't see the Halo of the Sun). The head moans and breathes quite heavily. Her eyes will light up and flicker if zapped by the stun gun.
Since the Otherworld in Silent Hill 4 is most likely caused by Walter Sullivan, it may be a reflection of his thoughts or psyche. Eileen was supposed to be another sacrifice, but she survived, which the scars may represent.
Her heavy breathing sounds as if she is using a breathing tube, like the ones used in hospitals. Her breathing may also be interpreted as being sexual and orgasmic, as if she is having sex or is masturbating. This could allude to conception and her role as a sacrifice, since she is the "Mother Reborn".