Thirty06,
The photo ID needs to be compliant with JAR-FCL1.015(a)(1) - what a mouthful! I assume a passport or photo driving licence would suffice. I still have an old paper driving one so I obtained a crew card from AOPA which is compliant. It also includes your Pilot Licence number. I think the LAA do one also. Just sticking a photo in yours will not be sufficient, as you point out it could be easily switched.