While most people think primarily of papers or photos, archival documents come in all forms. One of the most impressive textile 'documents' I can think of is the AIDS Memorial Quilt, now viewable online. It takes a minute to load, but it's well worth the wait. Be sure to use the tool to zoom on individual panels.
While the CLGA doesn't have anything quite this big, we do have a substantial collection of t-shirts, banners, and flags.