Based on metabox docs, I am unable to use other forms of image fields (e.g. image upload, image advanced, single image) because they all require user permissions (i.e user needs to be logged in). My form is used on the frontend before a user is logged in and does not have any edit capabilities.
Ok, hopefully the dev team solves this bug soon, because setting 'Required' to the field has no effect at all. I see that the code adds a data-required attr, but it should be adding a required attr.