Curious about this -- I'm not a buyer of such things. A growing trend online that has been booming is females selling pictures of their feet online, very often to male buyers. If the seller happens to be a minor, is this illegal? Feet can be sexualized but it is not a part of the body that is considered nudity -- you could also sell "hand pics," "ear pics," "stomach pics," etc.
But given the popularity of foot fetishism as the #1 fetish there is, feet remain most popular. What's the deal here though? If someone over 18 purchased "feet pics" from someone under 18 who willingly sold them of their own free will, is this a crime?
Minor is a term for anyone under 18 in the States you could argue, but what merit does that have for something of this nature? Just to note that this referring to the act of the purchase/sale of content, not of anything outside the nature of the transaction itself. Like for example it's obvious this does not imply a close relationship with a minor that is sexual just by means of buying said content any more than this would with an adult also if the only details surrounding such an act is of purchase and nothing further/personal.
Some imply this is "foot porn" but images of feet pics alone are not illegal to view, possess or purchase in any common situation.