In general, InfoPath attachments and images are embedded into the XML, thus increasing the size of the form.
Whether DBXL is involved or not, we recommend using qRules to extract those attachments from the XML and into a separate location. In the case of a SharePoint location, the file/image attachment would be extracted into a separate document library. (here's a video demo) In the case of DBXL, the image/file attachment is extracted into a separate document type.
Hope this helps!