100% quality Jpeg > PNG. There really isn't a lot of difference to make up for the significantly larger size of memroy it takes.
Eagles did you make the planets yourself? Or are they stock. It would be fantastic if you could post the stocks.
The first thing i ntoice is that the text is really distracting it doesn't blend in at all. THis is a space peice, no? Then the text should be sci-fi looking. Not fancy script looking. use something like fire eye GF or Agency FB. Very techy and would look great in this.
The colors don't rly match either, the red of the planet and the blue of the stars and the green of the plane. Argh, too many contrasting colors.
OH yeah ansd the lighting from the airplane is slightly off. It'd make more sense if you had reverse the plane.
Other than that though its not bad.
Just needs a bit of refineent.