Signatures, also known as siggies, are images that NaNoers place at the bottoms of their posts to identify each other. Usually they include quotes from favorite books, authors, movies, or TV shows. During NaNoWriMo, they are sometimes also used to promote the NaNoer's book. NaNoWriMo rules dictate that signatures be no larger than 500 by 100.
Some users also use banners, which are smaller (100 by 90) and usually used to identify the NaNoers sexuality and/or opinion toward LGBT+ issues.