I’ve switched the default user Avatar from the WP Wavater to the WP Identicon. I found that many of the Wavatar avatars looked pretty grumpy, and that really isn’t appropriate. The Identicons are much more neutral.
But, if you participate in other forums or discussions, especially WP based ones, you might want to take a few minutes to setup your own Gravatar icon. Note that the Identicon and other WP auto-avatars are based on your e-mail address, and actually generated by Gravatar.com, so should be the same on other WP sites that use Identicon.
From the Forum Help post:
User Avatar: You will notice that the Forum uses Avatars for all users. The Forum will use your Gravatar avatar. You can setup your Gravater at Gravatar.com. This is the only web based avatar the Forum will use. If you don’t have a Gravatar, the Weaver Support Forum will use the WP Identicon generated avatar.