ok well my advice to u would be to make it a more rounded craft. At the moment its rather 'blocky'. I guess it could also do with a top fin at the back. Also maybe u could add some more wings, think X-wing style. U might want to shorthen the nose also.

Try to keep the wing and fin proportions different to the that of a plane.

My best advice would be for u to search for spaceship references. Im not too sure what style ur after but looking at some sci-fi films will give u a better understanding of craft structures. That and imagination will help u no end

Nice work...keep at it