A general purpose polygon series would be nice, the idea being to show multiple regions with an assigned 'value'. Each region comprises one or more polygons.

These are increasingly popular for showing metric data regarding geographic regions (e.g. GDP by country) even in the absence of a proper GIS context, and provide a nice way to implement non-regular (e.g. hex or non-axis-aligned) heat maps. (I long ago implemented a similar thing for a hexagonal heatmap for a cellular model, so that's the use-case from which I'm coming to this)

A basic implementation is at https://github.com/VisualMelon/oxyplot/tree/PolygonSeries

Open design issues:

• Where should labels go?
• What should the label formatter look like?
• We should be able to attach a label to each poly (e.g. name of geographic region)
• Should polys have a user-specified logical center? (e.g. for tracker snapping; this makes sense for e.g. non-regular heatmaps where the value is sampled at a particular point but represented over an area)
• How can we support polys with holes in them?

Other:

• Would be nice to have a geographical example, but I've not bothered to track down any open data