Some people don’t use Gravatar, some don’t use Twitter and there are some who don’t use Facebook also and when they leave comment on your blog they leave a mystery man image (or your site’s default avatar) in their comment which sometimes does’t look nice. But you can allow them to choose their comment avatars manually by selecting a avatar from their social profile, email or choosing it from a list of your site’s custom avatars. I know about few plugins that allows you to do so.
Incarnate for WordPress
Although for this plugin WordPress show a warning that it hasn’t been updated from over two years but it works really very nice without creating any conflict. Very light plugin of about 40.9 KB. After you install and activate it, it starts displaying text box for entering email or alias of any social profile and it will automatically grab the avatar of the commenter. For example: If I type my full Gmail address then it will automatically grab my profile picture associated with my Google account. Its easy and powerful. See the following image:
It brings a rich avatar experience to WordPress comments. Commenter can select comment avatar from Facebook, Twitter, YouTube, MySpace and Gravatar.
Other than this if you like to add some custom avatars to your site so that the commenters can easily select an avatar to use on their comment then check out the following WordPress plugin:
Custom Avatars For Comments
As I had already said that this plugin allows custom avatars for every comment. After installing and activating the plugin upload your custom avatars to the the wp-content/commentavatars/ directory it also includes various configuration options as shown in the following image: