There's Mauretania fittings out there yet. I saw a show on PBS (don't remember the name) that featured a quick glimpse at a pub or restaurant in Bristol, England that had re-used the paneling from one of the public rooms. (And I've searched the web ever since to find out more information and have found zip, zilch, nothing... if there are any farflung Cruisemates out there who have any info on this restaurant I'd love to hear about it!)
If you notice, though, the current specialty restaurants all represent lines that no longer exist; the United States (US Line), Normandie, (TRANSAT) and Olympic (White Star, which merged with Cunard several years later).
So while there may be bits of the beautiful 1937 Nieuw Amsterdam (scrapped in 1974) out there, Celebrity may not want to advertise the heritaga of Holland America, one of their current competitors!