Is it possible to make a custom map in Google Maps API v3?

I'm working on a personal project involving map-making tools for a tabletop game that I play. I've worked with Google Maps in the past before, and it looks like in version 3 of the API, they have removed the API key restriction.

I have done some research into making a custom map, and have come across this page on mapki, but the example seems to be focussed on creating new tiles for existing real-world coordinates.

Is it possible to make custom maps that are not dependent on real-world coordinates in the Google Maps API v3?

(Slight tangent: If it is not possible to do this, what othe开发者_JS百科r tools exist to make custom maps?)

You could look at OpenLayers. I get the impression it's used a lot in the OpenStreetMaps community.

OpenLayers makes it easy to put a dynamic map in any web page. It can display map tiles and markers loaded from any source. OpenLayers has been developed to further the use of geographic information of all kinds. OpenLayers is completely free, Open Source JavaScript, released under the 2-clause BSD License (also known as the FreeBSD).

You could use Mapnik to render the tiles and serve them yourself. The OSM wiki has lots of documentation on doing that sort of thing.