Answer
With access to the Aurena Client, the supported path is importing the image through the Report Images > Images page in Aurena. Without Aurena Client access, there are two fallback options: place the image files under <IFS_HOME>\repository\server\reports\images\<MODULE>\<REPORT_ID>\ on the application server, then do a reconfiguration with the 'import layouts' checkbox ticked, which loads the images into the database (and mirror the same files into Build Home so they're captured for future deployments too). If even running the installer/reconfiguration isn't an option, copy the same <MODULE>\<REPORT_ID>\images* folder structure into a report_designer_graphics folder at the location pointed to by the 'Fallback image path' system parameter — this makes the runtime pull the image from disk as a fallback rather than from the database.