I mostly made this from the tutorial found here [link]
Unfortunetly, its not finished yet. I only saw this contest yesterday, and it ends tonight. I'm still submitting it though. It's taking me alot of time since it's officially my first digital piece of work. Hopefully you'll like it. I'll be finishing it in the next few days adding a couple of elements to it.
Original size: 3000x2250
Brush for nebula: [link]