I would personally advise against the head; adding gore to your piece would turn me away from it more than feel more frightened.
Note: Personal Opinions ALL THE WAY through here.

This is just my personal opinion, but I find that gore, unless it is the focus of the piece/theme/scenario from the beginning , is the worst way to generate fear. Sure, no one wants to watch gore but it is very blunt and to the point; there is no suspense, anxiety, or provocation of thought to consume you.

So, still just my opinion, but I would try and impliment something subtle but creepy.

Ex. To try and explain what I mean. What would you find scarier/more terrifying/had a bigger impact:
Watching someone be grabbed by [insert monster or horror villain of choice] and having their arm cut off
or
Watching someone be taken away, but see them partially come back struggling to hold onto something, then taken away completely followed by blood-curtling screams.
I find that thrill/fright/suspense comes from having your audience be able to interpret the worst thing imaginable. Because, more than likely, they will think of something much, much worse than anything you could have showed them upfront.

So relating it back to your piece, is there a way to imply that dwayna's been be-headed without showing her severed head, or corpse? Possibly something along the lines of crushing part of the headress she wears here? Perhaps even having feathers drifting out of his hand [blood could be lightly applied to them, to show they arent just assorted feathers but feathers of something dead] could be enough.

That way you know that she's dead, but you don't know how she died. You may think of beheaded, someone else may think of being skinned. Skinned would be much worse IMO, yet would be too violent to depict and would negatively impact the piece.
Alright, opinions done

Hope that helped, even to just create a spark in your brain. A spark is the first step to having a blazing fire