Custom Image fields can be added by clicking on the Plus button in the (Global) Fields manager, and selecting the option Image in the dropdown menu.
The event organizers can edit the name of the field (e.g. Profile picture), the label for the field which is visible to contacts and participants (which may or may not be the same as name of the field), and the category the field belongs to (e.g. Personal information).
The aspect ratio, max width, and max height of the image can be limited in the Validation category.