This all has a very Starcraft feel to it. The ships designs needless to say seem to be a thad bit generic. Complicating the issue are the “greebles” on the ship surfaces. Not that using them is bad, but using them in a gratuitous manner were it is obvious they serve no other function then decoration takes away from your image.
I think some fundamental issues should be dealth with concerning the ships. What is their purpose, what do they do, how do they move, how do they “work” in a real day to day pragmatic sense, are all questions you should be asking.
I would recommend that you perhaps take a step back, and concentrate on making a composition sketch that puts on paper what they IDEA of your image is. Remeber that an opera is driven by human drama, and it is VERY hard to have human drama without plot. As this relates to an image, particularlly illustrative images, is find a way of telling a visual story. Have in mind that the viewer will be asking themself why they should care at all about any of these ships, or the fate of any humans that may be inside.
Give this some consideration and I think your work will be alot better.