Or painting? Yikes. Here on FR in a thread discussing the new Christmas stamp someone posted Leonardo di Vinci's painting of Madonna and Child with a Carnation instead of Luini's The Madonna of the Carnation (which was used on this year's stamp). Leonardo's painting had Jesus naked. Yep, right here on FR "Divine Child Porn".
Imagine the ISP or local Wi-Fi provider of every single Freeper viewing that thread having to examine that painting and determine "Child porn or legitimate artwork".
Yep, it’s totally unenforceable, as you said. But the idiots will probably keep trying though until they get something workable, but no doubt equally objectionable.