Can you trigger a script with system.opc.readValue and directly grab the bytestring from the device?
I have grabbed images off a Datalogic Matrix Barcode reader over OPCUA as bytestring, but they came from a OPCUA method as a bytestring.
Once you do that, I threw them into a db as base64 and used them in reports:
@pturmel has a Blob server driver that will give you better options for using the images.