A little bird once told me that it's possible to add your own custom planet images, presumably that would show up in the inventory and inside the galaxy map index an so on. Also I heard that it's possible to change the backdrop image of a controlled system. Is this right? and how would you go about doing it I wonder??
Yes. You get the images made in the appropiate formats, and then make a new thread in the Art forum giving the planet/system ids for them. Once the planet/system owner has confirmed that its ok, the art team will upload as soon as possible.