1920's Mens Sweater History - 1928- By the late 1920′s the trend was for small patterns on mens sweaters. They were still gaudy but tamer color combinations than the mid years. http://www.vintagedancer.com/1920s/1920s-mens-sweaters/
Men (at least the highly fashionable ones) wore many accessories in the 1920s. Notice the different types of hats (here we see fedoras, straw boaters, and Newsboy hats). Canes were popular accessories as well as small rings, tie pins, and collar pins.
Mid 1920s 'Jazz Suits' were trendy because after WWI, people started to live a different lifestyle that led away from the formal three piece suit with shoulder pads. Life became edgier, more party-like and men dressed in simpler clothing, with hats, and fashionable chastises to go out dancing and partying.