[appearance] Transparency of the map
The color of a territory on the map is, now, a uniform color without particular background.
A way to greatly improve the appearance of the game would be to make the territory's color partially transparentand let the background be seen.
For example a map creator on an Earth map could put a satellite picture of the planet as background (fitting with the map of course). When a player with red color occupies a territory, this territory would just look like the background corresponding portion, but with a red hue added on it.
Neutral territories could be totally transparent while they haven't been conquered yet.
I know it might require to change the map-making format, but I think it would greatly improve how the game looks.