Hi Elisheba! Love your colors and shapes! When I zoom out and look at the piece, everything seems to work really well together.
I think one thing would be to create some depth to your piece. Right now everything seems to be on one plane. Maybe if you had some things overlap? Like stardust covering a part of the moon? Or make the spaceship larger so that it covers a small portion of the moon? You can also try blurring some of the edges of things that are further away while keeping things are close really sharp.
The orange planet stands out a lot, too, since it's the only warm object in a mostly cool picture. Maybe make it more desaturated or make the aliens orange instead?
I'm still figuring out how to make good compositions, too, so take everything I say with a grain of salt! You're doing great!