Thread:Epic146/@comment-3528596-20171017023344/@comment-104549-20171124004730

You'd probably do best to say something like "Created by user at this link". That acknowledges that you created it (thus explaining why that exact image doesn't exist anywhere else) but also gives due credit to the creator of the source code.

If you're claiming fair use, you'd probably do best to use the more specific screenshot template than the more general fair use one.

Add the required Information template, tweak the source, correct the license, and you'll be all set.