Design your own using real spaceships, limited as they are, as reference-material combined with your imagination and understanding of basic physics?
Lots of films have really bad concept art from a technical point of view anyway.
Or maybe set yourself a challenge of trying to make a primitive-object look like a spaceship based on textures and shaders alone?
Does the spaceship ever land on a planet? Or was it assembled in space and that is its only domain?
Does it have advanced technology that allows it to slow down whilst still in space which in turn allows it to land on planets without the need for heat shields etc?
The list could go on, but the answers affect the design of your spaceship.
Independence day: Resurgence had some awful concept art. They reverse engineered the alien space craft and yet still ended up with two separate aircraft. A helicopter without rotors and a fighter-plane that had wings. If you can hover and go into space and re-enter without burning up in the atmosphere, you don’t need wings and if you can do all those things without rotors, why have all the dorky attributes associated with something with rotors.
Surely it is better that it is your own work regardless of whether it is any good or not?