The Unsecured Access setting in the Advanced App Builder allows images collected through your App to be viewed by anyone, not just people who have GoCanvas accounts.
By default all image fields are secured access only. If you do a Submission and export your data (either from the Submissions page of GoCanvas or through an integration such as Zapier), you will get a link for each of your images. If you click on that link and are not logged into GoCanvas, it will show an error message that says "You are not authorized to access this data."
Turning on Unsecured Access
This setting appears on a field-by-field basis in the App Builder. Click on the image field you're using and select More. Then click the checkbox next to Unsecured Access.
This will not affect previous Submissions you have already uploaded. If you need to retroactively grant unsecured access to your Submissions, please contact the GoCanvas Support Team.