I change my avatar constantly. I do it to show off the things I like and because I'm great at finding and resizing images. Seriously, I have a ton of images on my computer that I'm ready to use. It's like a little hobby of mine.
For Halloween, I chose a fat kid eating candy because candy is one of the themes of Halloween. Earlier this week, I celebrated Día de los Muertos early by using a guitar-playing colorful skeleton enemy from Rayman Legends as my avatar because skeletons are popular with that holiday and I like Rayman Legends.
I usually change my avatar once a week and every month, I follow a different theme. For example, last September I had four of the six male pygmies from the comic book, Pocket God as my avatar (their names are Ooga, Booga, Dooby, and Nooby). In October, I had various zombies from Plants vs. Zombies 2 as my avatar. What theme is my avatar going to be for November? Stay tuned and find out.
EDIT: Now that it's November, I might as well say what my avatar theme is for this month. In continuation of my Pocket God theme back in September, my avatar will be four of the six female pygmies from the comic book. The first week is Kinsee, who doesn't get along well with the boys; especially tough guy Booga. In addition, my signature will also pertain to my avatar. I'll show off the remaining boy and girl pygmies in January. December is when I get into the Christmas spirit.