I'm curious to see a version of this which accounts for changes in Eurovision over time. Clearly, the current version is influenced primarily by which countries have participated for the longest, and so relatively strong Eurovision countries that have only debuted recently, such as Azerbaijan, still appear in a low position. In order to properly show the average performance of all the countries, I can think of three things to adjust: dividing each country's score by the number of years they have participated, accounting for the number of countries voting in each year (so that participants in the earlier years don't have a lower average due to only having 10 countries voting on them instead of 40), and normalising the voting system, which from memory has not always used the 12-1 scoring method.
The first of those things is easy to do, but the other two would take some thinking...