Our old set of community avatars is being refreshed. We'll start the gradual process of replacing the old avatars with new avatars. This will be a one to one exchange so if you are using a community provided avatar, you'll notice the change on your account.
You need to do nothing. The avatars will be changed out in the background. The exchange will take a while so don't panic if you don't get a new avatar right away. The first round of avatar replacements will start with the PEOPLE group of avatars. If you don't like your avatar after the change, feel free to choose another. Here is an example of the new community "people" avatars: