Creating a dedicated showcase like L.Dutch suggests is a great idea. It provides clear structure, and community support to sharing our creations. Keeping it centralized means that everyone's work will be equally discoverable. Similar to the sandbox that will also make it easier to inform people about any policy or usage guidelines.
Before creating The Showcase we should probably figure out how exactly we want it to be used. Starting with some clarity of vision should help provide a consistent experience, both for people sharing their creations, and people wanting to discover what the brilliant minds of this site have produced.
Additionally we should also encourage people to share their work on The Factory Floor and in their profiles.
The factory floor is great for works in progress. Chat provides a far less structured environment, while still granting access to the creative minds of Worldbuilding's community. This is especially useful if someone is looking for discussion, or help with brainstorming, story, characters, or any other task that isn't suitable for the main site. I don't think a showcase will be the best place to seek feedback while iterating on a work. Something more ephemeral and immediate, like chat, should help keep those creative juices flowing.
Including links to work you are proud of in your profile is less discoverable than the showcase. However it will always be directly associated with everything you do on this site. If someone finds a particularly inspired question, or inciteful answer, the author's profile is just one click away.
Creating a showcase in conjunction with encouraging the use of profiles and, and chat seems like the best way to give people recognition for their hard work. We should try to be deliberate with how we structure the showcase. If this post is well received I'll create a separate question to seek community input on how exactly we want a showcase to work.