In order for your derivative work to be kosher, you need to do two things:
1. Attribute the works that you're using to the wiki and to the specific author, if possible. For example:
682's Lovely Tea Party is based on "SCP-682" by "Dr Gears": http://scp-wiki.wikidot.com/scp-682
2. Add the Creative Commons Attribution-ShareAlike 3.0 license (or CC-BY-SA for short) to the derived work. Doing this will release it under the CC-BY-SA license.
Releasing it under the CC-BY-SA license means that people will be able to copy your work wholesale, and even sell it, provided that they properly attribute you and release their work under the same license.
Also, do not sell SCP-173-related stuff. Please. It's a massive headache for all parties involved. And might get you sued, depending on the context. Just don't.
Hopefully that wasn't overly intimidating or confusing. If you have any questions or concerns, feel free to contact our License Experts team!