Here's a quick project I've been working, for my own use, shared here for others who may be interested. It's a basic map editor for Inform 7.
It lets you visually layout your maps, then exports the Inform code (which is basically English), for use in the Inform editor.
It's very basically currently and may have some bugs, though I'm providing the capx here so others can edit it if needed.
Try it out here: TRY IT
And the capx:
I think it could come in handy for anyone looking to create a basic map editor. The size of the grid is very easy to adjust, it's purely based on the dimensions of the Tile object. It'll calculate the number of rows/columns based on the layout dimensions.
I've since realized a far more elegant way to achieve this one so I'll be working toward that rather than continuing this one, methinks.