If you go on the imdb link I sent, you will see one poster that has an image of an arm with a knife swooping down, and the image of a screaming woman's face in the reflection of the blade. I'm not 100% sure if this is an official 'Nightmare' poster, though I do think it would be the most appropriate. The tagline appears to say "The screams you hear...could be your own!!"
I'm sure I've heard that tagline somewhere... even still. I think this is the best poster.http://www.imdb.com/media/rm1470536960/tt0082818