1/ The ships seem to stand 'out' a bit against the background... look a bit 'off' as a result. I'm not a big fan of the BG, actullay.
2/ Something seems 'off' about the lighting..not sure what, but maybe cos there are very large shadowed areas, and large bright areas, and not much transition between the 2... which seems odd
3/ Violet/blueish blob is too round...I think it's the shield, but it's too flat and regular IMO... maybe needs to 'curve' around the ship a bit. i'm not sure how I'd do it myself, but maybe a sort of 'cutout' bit of a cylinder, with a opaque selfilluminated map
4/ There's no real sense of motion, IMO....it seems..static, I guess.