for both versions of the image, you need to have a hidden form element on the page.
set the initial value of the first hidden form element to use the large image column value from your recordset.
set the second hidden element to use the mini image column value from your recprdset.
In the upload file behavior, select the large image, set the default file name to use the first hidden form element.
select the mini image, and set the default file name to use the second hidden form element.