The overall design is good, I like it a lot especially the emblem overlay on the planet. The only things that let you down is the inconsistent lighting angles (planet - light from right side, ship - light from left side) and perhaps the rushed engine trail job (?)
You can enhance the trail a little by adding a glow onto it but you'd have to reset your light in your render to keep it the same as your background. To make the lighting perfect, use a light source (top right corner) and go over the left most edges with a low opacity soft black brush.
Yes, I like to pick up small details because I'm an artist myself and notice them as I design my signatures.