I did not just plaster his texture over my models but redrew it but tried to stay to the original color scheme.
They looked photomapped to me, too.
You need to start over again, using clean edges and sharper line-work, with more greebling and nice, straight lines. If you haven't planar-mapped the flat surfaces, you should do so, instead of ending up with wobbly lines. These are very flat models, that should be OK for most areas, aside from the engines and "pods", which need to be unfolded. Planar maps are there for a reason
You're working from tiny concept sketches- other than general areas of color, there isn't any reason to take them literally. I'd like to see a lot more attention to functional details.
Also, if you're going to keep the really thick blacklining, then it needs to serve some sort of real purpose, imo. Use a bevel to suggest it's a raised sectional edge, or something...
[EDIT] now that I've looked at your painting... meh... you need to learn how to keep your painting cleaned up... no wonder you cannot keep your lines straight, you can't see where an object ends or begins very well. Here is what one of my maps looks like:
Basically, I take all shapes on the uvmap, select them, expand the selection by 3 pixels, then make a layer via Cut... it helps tremendously, if you know where your objects are, and their real shapes, at all times. If you need to know the exact positions of the polygons, then you just use a semitransparent set of lines using Inverse as a layer on top of everything else. Much easier than painting like you did, with sloppy airbrushing everywhere, and you never accidentally paint what you don't want to, if you use Magic Wand to keep your selections clean.