Greetings,
Please if it so pleases you to do so, what is the data connection type that is used for the scanned .jpg to the sharepoint list.
If the infopath signature field is a picture or file attachment (base64).
And the sharepoint list is a picture library.
A recieve - from sharepoint library or list - doesn't allow the "name" field that contains the .jpg to show in the field list or be selected as part of the data connection.
Thank you.