How can I create a custom avatar and generate artwork based on it? [closed]

I need some light on how to create a tool that allows a person to customize an avatar and then generate a set of different artwork based on it. There’s an online tool that allows you to do it:

HTML form with a field to input a name

You can input your name there and when you click the button you can start to customize the avatar:

avatar customization

In the end, some images are generated based on the avatar:

generated images based on the avatar

How can I start building something like that? Any references to read?