By default, WordPress shows Gravatar image of the users as their profile picture. If a person is not having a Gravatar account, he or she can choose from the default avatar types on the site.
Do you want to create unique avatars for all users? It should display the first letter in username instead of their photo or generic logo.
WP First Letter Avatar is a good custom user avatar plugin to replace Gravatar profile images in WordPress. It is simple, light-weight plugin that will reduce your page loading time as well.
It provides beautiful, colorful user avatars in many sizes and they are automatically optimized using TinyPNG. So all users will get high-quality letter avatars in author bio and comments. The plugin is flexible and decide whether you want to use it with Gravatar or as alone.
After installation, it will add a new submenu in your WordPress dashboard. Open Settings > WP First Letter Avatar to configure the plugin.
Letter index field shows 0 as default. It means users will get the first letter in their name as avatar image. If you want to replace it with the second letter in the user’s name, enter ‘1’ there. ‘-1’ represents the last letter in the user’s name.
Specify your file format, image name for unknown users, avatar directory in the following fields. To allow Gravatar users to use their respective profile images, check ‘Use Gravatar’ box. If you want to replace everything with first letter avatar, uncheck the box.
Round avatars is the next option. It allows you to show rounded avatars for all users. But the feature may not work sometimes as your theme may override this setting. Plugin filter priority lets you set priority for WP First Letter Avatar over other similar plugins. The value ‘1’ indicates top priority whereas ’10’ represents lower priority.