Bitstrips dresses are all over the site. They are usually made out of shapes and/or props from the Art Library in the "Comic Builder."
Making characters Naked.Edit
In 2008, the Devs added a new feature that allowed a user to make charcters naked, which was used by many users to make dresses. Due to complaining users and parents, the feature was removed by the Devs. A glitch in the Comic Builder allows users who joined before 2011 still make naked characters. It is also said that there is another way to make naked characters, by adding parts to a link, that can only be used for the old character builder characters.
How to make dressesEdit
If you want to learn how to make dresses you should probably search some dress tutorials. A dress tutorial is a comic of a tutorial on how to make a dress. In a dress tutroial, the maker usually picks a model, has some steps, And wala! They're done. The main goal of a dress tutorial is to teach the reader how to make a decent dress. Here is one of my favorite dress tutorials, that I learned much from. (Link)