Most of the whole item + "not much else".
Meaning, the thumbnail that buyers see when browsing search results or categories is so small - don't waste precious real estate with clutter around the item, or blank space.
For earrings, often my first shot thumbnail excludes the earwire, focusing on the main gems part - so you get 80% of the item. For necklaces, pendants, I focus on the drop/bib/gem part also, rather than a far-away shot of the whole necklace - that's inside the listing. So I think there are exceptions.