Here is an image from SW:IW. Most of the structures have the same grey-style background as your turret. The addition of things like vents, grates, circuitry, armor plates, or any other common "greebles" bring the texture to life.
So as GMN said, you've got a nice looking background, just needs a bit of variation and detail. Be weary of random and thoughtless greebling as it will only make your textures look disorganized and unrealistic.
Painted on light and bloom (around the glowey areas) for one. Do something to break it up, its all the same boring grey, it will look like a grey stick zoomed out!