So yeah it lacks details. Moar details yo...
If i were you , i will add more asteroids , it need alot of asteroids and planetoids orbiting or circling around the sun [Asteroid Belt]. There're alot of asteroids in the Models Section here in Hive , pick some then import it to your terrain.
The sun seems not that good,maybe because the centerglow[the white part] of the sun's too powerful , lessen that abit , reduce the white or just make it smaller.
The sun rays seems not directional , i feel like the rays are coming from the wrong source, i dont know.
Remove that big tower at the front , it's really attracting , and is not good.
The planet seems fine for me , it just need some tinting , make it a bit darker. You must also rotate that planet , i know it has a shadow behind. Look at the light source , note that the light source is coming from the topper left [the place where you placed the sun] , not from the camera , so it must face the topper left or the sun.
The flares , i think they are fine, just tint them down abit , lesser visibility.
Nebulas are'nt that good , make more variations of it, more colors! You can also use the Ubercloud as a Nebula if you want.
You can place more planets , maybe add the Jupiter, Earth, Uranus and Mars.
For the positive side , it is great actually , i remember my galaxy terrain [but i didnt released it because it really looks bad]. I like the front part of the station and the stars. I also like the idea of making a dockway for the space collectors.
EDIT:
You can adapt some ideas here
http://www.hiveworkshop.com/forums/members/226575-albums7453-picture88608.html
-Lasers bro , it give details and coolness to space ships and it also shows sci fi feeling.
http://www.hiveworkshop.com/forums/members/226575-albums7453-picture88617.html
-Yo , that's what i'm talking about. You can use the Uberclouds as a raplacement or let's say , they are bigger Nebulas. It also show proper facing of the planets , the lighter part must always look at the light source.
EDIT:
Sorry for bad english