Agnes, Lady Dixon-Hartland is pictured wearing an unusual tiara in a portrait taken by Bassano shortly after her wedding to Sir Frederick Dixon-Hartland in 1895; I have no additional information about the jewels pictured

The Princess of Wales (later Queen Alexandra) wears the tiara from her wedding gift parure in a portrait taken by Bassano in the Marlborough House conservatory, May 1881; learn more about the tiara over here!

Elizabeth Anna Lewis, Lady Merthyr wears a suite of coordinating jewels, including a tiara, in a portrait taken by Bassano at 25 Old Bond Street in London, July 1920; I have no additional information about the jewels