I changed the mod a bit for 0.14.5 rc2. The original was more like a proof of concept and had all planets render a huge polygon that covered the screen in full transparency. The good thing is you could take transparent screenshots anywhere there was a planet in the background, the downside is that the background colors were blended with the ship, which was especially visible on the half-transparent missile trails.
So in version 2, you go instead to creative mode and pick a fake galaxy size from the list. They will drop you in a sector with no galaxy and white, gray or black background where you can setup your ship(s) for the screenshot.