1, 6, 7 and 9 look pretty cool to me :) have you seen the film Elysium, could do something Silmilar with your loops :)
Yeah I have, I have a few images from it in my influence maps...Simon also mentioned Elysium to me, I might rewatch it since it's been a long time since I've seen it.
Halo is always a good point of reference for stuff like this too. If you're going for sleek stuff, then look at the covenant ships in particular.
My favourites are numbers 1,10 and 12! Look very unique!