Why not pick a decade and base your fancy dress party on that era. The popular themes are 1920s, 1930s, 1940s, 1950s, 1960s, 1970s, 1980s and the 1990s. Simply pick famous people from that period or famous fashion phases. The 60s and 70s were best known for the hippies, that would make for a very colourful party full of world loving, peace promoters dressed in flower power patterns. Surely that is going to be a great party!