Customer Picture image in sales page

Where are we storing Customer's pictures?

Better still, create a new table called, say, customer_images and link it on a 1 : N relationship with the debtors_master table and have a timestamp field in the new table as the date of last update and use the latest photo in it to display in the invoice form. Possibly have and show a signature field as well to have their scanned signatures for verification.

debtor_id INT AUTOINCREMENT NOT NULL PRIMARY KEY
lupdate DATETIME
Picture BLOB
PictureType enum ('Photo', 'Signature')
IsDeleted TINYINT DEFAULT 0

This way, when there is an FA Upgrade, your table will not be affected.

You will need to show it in a popup window when an invoice is being created or editied or viewed. So code a separate php page to show it and pass it a variables like debtor_id, company#, logged_in_user, logged_in_token, etc. - check if the said user is logged in and the token matches and then pop up the window.