Eiffel Tower is a public architectural monument that can't be protected under copyright law. As we mentioned in a previous entry, shooting and reselling publicly visible architecture is almost always permitted. As for the LOVE sculpture by artist Robert Indiana, that is not protected under copyright law because the Copyright Office apparently refused to register the work, claiming that the law does not protect single words. Typically, however, public murals and sculptures are protected by copyright law.
Why you should take it down. We talked about the rights of mural artists in a previous entry and explained how mural artists are protected not just by copyright law, but also by some state art laws. Merely creating the mural doesn't mean that the complainer owns the copyright -- the mural may have been a work made for hire or the copyright may have been assigned. Chances are good, however, that if he's complaining, he's the owner -- why else hassle you? The copyright owner could file a DMCA complaint with Etsy (or Etsy's ISP) or could sue you (or both). If you can make this situation go away by just removing the offending photos, that would be the most efficient course of action.