The bottom of my form there is a place to add up to 3 pictures and a signature box. I submitted the form with all information but didn't add any photos but I did sign it. When I went back to edit it, I can edit everything but I can't add no photos and my signature is gone and want let me sign it.
Survey123 does not currently support editing of attachments via the Inbox.
Having said that, please take a look at the following response on a different GeoNet thread in which Philip Wilson explains how you can add images from the Inbox when the question is contained within a repeat.