Block previews - Sage 10 + ACF Composer

As the title suggest I am using sage 10 with ACF Composer.

See the following link for an example of how to add a custom block. Its not detailed in the docs but there is a block preview that can be generated by adding some data. It works if I give it dummy data that matches the fields() section, however I want to pass the preview and image url.

     * The block preview example data.
     * @var array
    public $example = [
        'attributes' => [
            'mode' => 'preview',
            'data' => [
                'preview_image' => '',

My current attempt does not work.

Anyone had any success adding preview images?

Thanks in advance.

Are you referring to the preview popup that appears when you hover over a block tile? If so, I don’t believe you can pass an image value to it as it’s dynamically generated based on your block markup.

Yep, that preview.

Was hoping an image would work. Will pass it markup instead. Thanks