Unfortunately, you can't upload your own avatar to the Animate from Audio editor. But you can upload your own background images to use in your videos. That process and the whole process of making a video with Animate from Audio is demonstrated in the video that is embedded below.
Video - How to Use Custom Backgrounds in Animate from Audio
Applications for Education
Like I did in the video above, by using custom backgrounds students can create short videos to explain the highlights of a famous (or not-so-famous) place.