Below an attempt to show what countries belong to what organisation. (A bit outdated, the UK has left the EU). A good start with the groupings of the countries, and the circular layout of the flags. Also note that flags are displayed in their correct aspect ratios (Switzerland for example is square).
What to do better?
Not a big fan of the gradients and shadows
I would put the Council of Europe label also on the right
It should be possible to get an even more harmonious and distributed layout by moving some flags, labels and circles around
The other approach to make this chart is to use a map and color code countries according to their memberships
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