Problem
The iTunes store doesn't currently block explicit images on album artwork regardless of the restricted content setting.

Solution
Explicit album artwork should follow the "Restrict: Music with explicit content" setting on both iOS and the desktop app

Personal story
While searching the iTunes store with my kids for an animated cartoon about "The Snowman," an album with a topless woman popped up as one of the search results, even though I have "Restrict: Music with explicit content" turned on. After reaching out to apple on the subject, they responded "Upon having multiple interactions with the appropriate team it was confirmed that it is an expected behavior.

For your information, the Restrictions that are set on devices will not impact visibility of album artwork. However, it can’t be accessed or purchased from iTunes Store until the restrictions are off. "

If I opt to not view or listen to explicit content, please don't show me explicit content.