Thread:Extension talk:Maps/Can a custom layer be used instead of a mapping service?

I saw something in the revision history about a custom layer placed in the Layers: namespace on a wiki and used with this extension. Would it be possible to make such a thing and use it as the map source? I'd like to map out a fantasy world rather than the real one. Pie-in-the-sky wishful thinking: could the Categories of the wiki be used in map queries? Thanks for listening :)