According to Dr. Jennifer Baumgartner, most people wear 20% of their closet 80% of the time. With that metric in mind, you probably have many clothes in decent condition and may get up to 80% of their cost.
Selling jewelry is a different ballgame depending on the type of jewelry you wish to trade. If you are considering selling expensive jewelry, you should get an appraisal by contacting The American Society of Appraisers.
Original vintage posters advertising products and events like movies are in high demand in recent years as nostalgia collectibles. Whether you have an original vintage poster or a collection, you may be able to sell them at an auction or gallery.