The docs here https://docs.avohq.io/2.0/fields/file.html

field :avatar, as: :file, is_image: true

recommend using this.

The is_image, is_audio, and is_video options are deprecated in favor of letting Active Storage figure out the type of the attachment. If Active Storage detects a file as an image, Avo will display it as an image. Same for audio and video files.

but this at the bottom says its depreciated. On my current version the image one display in the index without is_image.

you're right. you have to use

is_image

on the file field