Pretty cool. I really like your palette.
I could tell it was some kind of crashed rocket / jet built out of junk. If you want to make that more obvious, you could make that wing on the left side bigger. Aside from that, the ship looks good.
I don't know what you have planned for the background, but right now those trees are a little distracting, the way they seem to make a straight line across the top of the image. There doesn't seem to be any variation in height or distance.