How to add an avatar?
You may set the avatar for the chat user via the "blob_id" field. You will need to upload a file into the Content Module and then connect it to the user with the mentioned "blob_id" field, as it performs as a link to the uploaded file in the Content Module.
Please do not hesitate to check our SDK documentation regarding this matter:
How to add extra details?
In case you would like to display additional user details, you may create a class in Custom Objects (e.g., UserExtraProfile) and write all the extra fields of your user to this class. Other users can retrieve these fields with the "user_id" field filter in the "GET" request.
Please feel free to check our SDK documentation about this topic:
React Native: https://docs.quickblox.com/docs/react-native-custom-objects