Couple of things ; Nice that your trying your own nebulas etc. through the clouds, got a light source too which is a start. Your colours are a bit off, slapping a Photo Filter in a blue or something would balance the whole piece out and generally...help. Not a bad start though since your new to it, practice means everything with space scenes.
I agree with Broken. Personally I like everything a bit more in one color and way more sharpened But seriously it's looking good!
