If you project your planning into next year...

When you see a mask or makeup on sale OR once Halloween is over, buy a few sale costumes. Then, throughout the year, as you shoot content, bring some of the costumes with you to each shoot and have the models do a side shoot.

This time next year you'll have a good amount of Halloween content to use on your site, a bonus site, promo content or to sell off to those who run themed sites around the holidays.