I saw picture today of a Black Cat Pillow , and the article shows you how to take a simple plain black pillow and turn it into a Black Cat Halloween decoration by just adding buttons for they eyes and nose, along with embroidery floss to create the whiskers. I would think that you could also use items from the doll crafting area of the craft store if you wanted more realistic eyes . . . you could even use the ones that "google" around.
Then I started thinking why stop at black cats . . . get an orange pillow, cut a jack-o-lantern face out of black felt and if you want to make the project kid friendly you can use fabric glue instead of sewing the felt pieces on. What about a white pillow, and make a ghost face on it.