I appeared in class like this and caught my students by surprise. It was a worthy sight, let me tell you.
We made lots of photos, but I cannot post them - they are for our eyes only. Among them there were witches (of course), some mummies, ghosts and spiders. Working in several groups, they made skeleton and ghost garlands, carved some pumpkins, played 'pin the tail to the cat' and "Don't Eat Frank". It was a 'thrilling' day by all measures.
I have a Halloween board here if you are in need of ideas - for future Halloweens that is.