The 1920's encompassed the end of Art Noveau, the beginning and middle of Art Deco, Oriental and Egyptian revival pieces, as well as "flapper" styles, such as 100"+ strands of pearls - many strands of pearls. Platinum was the de rigeur of the period, and people were most interested in geometric and figural shapes. Emerald cut diamonds were especially popular. Large colorful gemstones were also in fashion. Wristwatches became practical, large cabochon emeralds and stones displaying asterism gained in popularity, and new techniques of enameling came about - guilloche etc.
Nothing was too gaudy for this period of incredible economic growth. And wow...that strass jewelry was AMAZING.