I think it would be worth adding a new example that shows 2 plots:

A scatter plot with 2D blobs data (e.g. 3 overlapping Gaussian blobs) with the initial rectagular grid overlayed on top of it (or at least the location of the grid nodes if drawing the grid edges is too cumbersome with matplotlib) + a second plot with the same data points but with the grid nodes matching the locations at the end of the SOM clustering. In the second point the data points could be colored with 3 colors as assigned by the SOM clustering process.