I'm acually trying to work on some holiday icons and my go to has been stuff that i personally associate with the holidays and what's commonly brought up.
Some of the themes or references in some sketches i've got are gift wrapping, candy canes, hot cocoa, "ugly" sweaters, ribbons, and a more fantasy inspired christmas spirit. Looking at bases or other folks holiday illustrations tend to help me get ideas or even looking through those shopping catalogs that tend to come around this time of year with the yule logs and kettle corn (I'll also definitely be using acnh's holiday event as inspiration as well)