The design of the room主语
was谓语
in the fancy style popular 表语
in those days定语poupular应该是和in those days在一起做一个成分的吧。The design of the room主语was谓语 in the fancy style表语popular in those days定语 您说的对。这句子完整的应该是The design of the room was in the fancy style （which is）popular in those days.谢谢啦！好棒！