. If my job were to think up ways to prevent something i would also try to think of the easiest ways to defeat my proposal just to make sure it’s not a stupid or useless rule

Even easier than that. Simply make "kid mode" that won't display a single image resulting in a text only phone that is fully in compliance with the demand. "Adult mode" would behave exactly as phones do today. Five minutes after a parent buys the phone and the kid figures out there are no pictures, the parent would enable "adult mode" and never look back.

I present you: the fully compliant phone.