Avatarly is described as 'simple gem for creating gmail-like user avatars based on user email or any other string passed' and is an app in the Development category. There are three alternatives to Avatarly for Online / Web-based and Self-Hosted solutions. The best alternative is Gravatar, which is free. Other great apps like Avatarly are Avatar (Free, Open Source) and Evatar (Free).
Evatar stands for email-linked avatar. Your evatar is an identifying picture that can be used to represent you on any website. Developers can use Evatar to seamlessly integrate user pictures that are effortlessly customizable.