Pretty awesome. Really liking the star field, overall look and variation in color. The only thing I can see is the edges of the dark cloud are very harsh in some areas which flattens the piece a little.
Holy crap, that's a long time! I've always wanted to make some of these but I can never find a decent tutorial. -.- I love your stuff so much! Maybe you should write a tutorial lol.
~ Lilith
looks like fractals in some regions, it's amazing