At first, I thought it was real, and then I opened it to see it in its full size, the star field looks realistic to me, but the nebula, not so much, but definitely not bad and it does have some realistic qualities to it :) At least it does in my opinion :) nice job!
I like the color but I think if you have a kpt plug-in using the noise or what you mey call the cloud effect which will give you the vains of light you may need to give it a more realistic feel. A good effort . Enjoy!