It's pretty common to have to show some form of state-issued ID when entering bars and the like in France if the bouncer thinks you're underage. Ditto for buying alcohol. Hell, in the US I've had to go back to the hotel to grab my passport to enter a bar. My French driver's license and balding head weren't enough.

But you do have a point about "storing the picture". I think that's why it's very important for whatever solution is chosen to be something that proves you're old enough without saying who you are.