In addition to the set of built-in figures and the optional Library figures that ship with Stykz, there are three ways (currently) to get additional figures for use in Stykz.
Get Them From the Stykz Community
Several sites have cropped up (and more will follow I'm sure) that provide forums for Stykz users to discuss topics and share Stykz Figure files (.styk) as well as Stykz documents (.stykz). The most popular of course is the home of Stykz, Stykz.net. There is a Stykz.net forum exclusively for posting and downloading Stykz files, so you can always go there to see what others have created.