It's a frequent problem that people paint up a cool ship that looks nice in Blender and Substance painter, but comes out dramatically different in FSO. This is for a lot of reasons, indirect lighting tech, rendering methods, tonemapping settings... but a big one is just lighting conditions. Every modern tool I've used, from asset production to showoff website uses HDRI, essentially skysphere textures encoding the real brightness of an entire environment, for at least part of their lighting solution. This kind of image based lighting is radically different from how FSO does lighting, but even worse than that is the fact that every HDRI library I can remember looking at is packed full of various well lit terrestrial environments but utterly lacking in space scenes both realistic and cinematic.
So in my recent graphics pipeline adventures I took a detour and made a skybox from the actual rendered sky of a FSU mission, specifically Surrender, Belisarius! I've tried it in Blender and P3D, and I've used similar things in Substance Painter in the past. The results aren't 1:1 matches by a long shot for all the reasons above, and because trying to emulate suns in the HDRI has proven challenging, but they're much better than the normal stuff. For example, here's Nyx's moloch(slightly screwed with for warmachine things) rendered in blender with a good approximation of FSO's shaders and whatever HDRI blender had on already
and the exact same thing, with the HDRI I made.
You can also see one of mine in use in the recent Herc p3d from MJN.
I would be surprised if using something like this doesn't make it a little easier to get good results out of FSO, but I haven't tackled a ship texture yet myself so let me know if you give it a try. I've included a version with a huge sun attempting to generate strong lighting, and a version without the sun, in case that's useful. I've also included a few different file sizes, in case you're laboring under size limits somewhere. And last I've included a seperate file of my source images and somewhat sloppy blender file, in case someone wants to try to improve on it.BackgroundsSource files
Lastly, if anyone thinks a different level would be useful for them, I am accepting requests. Mods are fine. Don't expect the rate of production to be high, but it's something I can do now and then.