... turns out too dark or way too light.
That does not necessarily have to do with the textures, in each ship entity file there is an entry that regulates how the ship is affected by lighting:
minShadow x
maxShadow y
x and y ranging from 0 to 1, the higher the number the brighter the texture can be.
If you increse the minshadow value ships will come out much brighter even when in full darkness, maxshadow influences the light from lightsources and such areas.
For my mod for example i wanted a grittier look on all ships and structures, with the effects more standing out, so i changed the values for all ships to min = 0 and max = 0.4 which gives a very nice overall look.
Here some sample images:
min and max 0

min and max 0.5

min and max 1

In the original beta the values interestingly vary wildly from ship to ship and especially very high min values sometimes overbrighten your ships when you zoom out.
These are some things i tried to fix and improve by adjusting the values in my mod and if you mod the textures you have to take these things into account aswell.