First of, avatars and attachments can be added to the Insight objects, I've attached some screenshots that shows where it can be done.
There is currently no build in support for bulk editing attachments or Avatars.
We do on the other hand have an open API, and there is one question already asked how to upload attachments, which you can read about at https://community.atlassian.com/t5/Marketplace-Apps-questions/Upload-attachment-using-Insight-REST-API/qaq-p/663186
Uploading Avatars is not however possible using the REST API.
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG
You're one step closer to meeting fellow Atlassian users at your local meet up. Learn more about AUGs