If you haven't already heard by now, April's theme month is that there is no theme month. Here's the story:
Theme months used to be something we did once in a while for special occasions. It started, if I remember correctly, with a Star Wars theme month on our original forums, and grew from there. But somewhere along the way we got into the habit of doing them every month, which kind of defeats the purpose.
So from now on theme months will not be monthly, but will appear every few months throughout the year. Say four a year: Christmas/holidays and three others at more or less random intervals. The next one will be in the summer, probably July.
This presents an opportunity for everyone to revert to their "default" avatars if they have them, and to choose them if they don't. I've alternated through a few regulars, but I've decided to settle on the green apple as my default. Brand image is important, after all. 
Joking aside, your avatar is your "face" on the forum, so for the sake of recognition it's nice to have a consistent one. They become your identity. I was shocked, for example, when I met Phate in person and he did not have a Companion Cube. But no, it turns out he's a balding, middle-aged trucker who just wanted to have angry, angry sex in the men's room stall.
And THAT'S why it's important to have a good avatar. Choose wisely.