I love Halloween costumes but the second thing that gets me counting the days to the 31st is the party décor. I would suggest to stick to a color palette for this too. A very cool color mix is black, white and orange. Here's an example from Sweet Little Peanut for Pottery Barn Kids. White chocolate apples, mason jar filled with orange soda, stripped straws, real pumpkins and orange and white balloons will create a really cool effect.
You can also design labels and tags for your beverages or candies like these from Fox in the Pine.