So first off we'd need an SVG of Europe - preferably with each of the
countries in separate shapes. Turns out that was very easy to find.
In Umbraco, my first thought was then to build a "repository" tree with the
selected countries. That way, the editor(s) could add a new content node for any
new country, and/or delete any node for a country that should no longer be highlighted.
If we could match up the ids (or more likely the aliases) with
in the SVG, it would be possible to switch them on and off in the SVG.
But then I realised that the SVG really has all the info - so why not do some
kind of lookup in that, and then just record the on/off state in Umbraco?