I bought the album for the music.  The cover almost made me not buy it.  The cover may be iconic, but I doubt it would have turned out that way if the music sucked.
It's problematic if the photo was used without the parents permission or any kind of release, but waiting 30 years to make an issue of it and claiming it's "pornography"... good luck.
There is no federal statute of limitations on child pornography, meaning the feds can step in at any time after the fact.  Also, federal law does not require any type of sex act, the simple picture of anyone under 18 and graphically naked is enough to satisfy breaking the law.

Furthermore any person who knowingly purchases the image is breaking the law as well.

State laws vary wildly.  Maybe time to buy a white sleeve and pitch the offending one.   LMAO.

Regards,
barts  
Another interesting angle:  If this is actually adjudicated as child porn then
what about Qobuz (for instance) showing the album cover when you play the album.  Is that distributing child porn?

Regards,
barts