What sort of creation? An entire game? No, although a well-made one could be sold on the Marketplace as a module. Note, that you could create an entire campaign and invite a player to it, and then give them GM rights. It would still be under your account, though. A map or token art? Roll20 frowns on this, as it impinges upon the Marketplace. They have stated that they wish to support and encourage creators to profit from the Marketplace. As a creative professional (though not in the Marketplace) I applaud this attitude. It's hard enough to make a living in this field. A script or macro? Yes. There are a great number of threads for these. Even ways in which you have used the tools in Roll20 to solve problems creatively are encouraged. A story idea or game system? No. Those are not primarily related to Roll20, which discourages talk not related to the site. A list of jukebox tracks? Yes. Something you've created that you want to show off visually? Yes. Several threads have been made to show off landing pages, for instance. This is related to how Roll20 is utilized. Note: This is my understanding. I don't represent Roll20 in any way.
