I've had fun turning our annual Halloween costume photos (a couple in 2013, 2014, and 2015) into an opportunity to learn and test ideas as I play with equipment and reach for looks that compliment our kids' chosen costumes for the year. I took the opportunity this year to play with flash gels and some strobe modifiers. The kids are game for it so I look forward to the Halloween photos every year.
I can't honestly say that I understand what our son's and middle daughter's costumes are, though I was told a literal Ninja Turtle in a tutu (apparently a Pinterest thing) and a mystery Badger (based on the school mascot and colors), respectively. I do recognize the witch theme though!