Unknown Structure

Looks like it is from a mod, there are also a few ships that aren't from the Vanilla game as well.

someones been having some fun, they look like the Ga'ould ships from Stargate SG1 and/or the Borg Assimilation Vessels from Star Trek Armada II, pretty cool if you ask me... 

Hopefully Ga'ould, I hate star trek last thing we need is another mod lol.

One of the ships in the pic is in the first trailer of this game.. even look!!!  http://www.youtube.com/watch?v=e2Pv7TtV8js right when the lage fleat is in it ..............  The first traid port in the pic right below it it is thare to so yeah its probobly frome a mod dude.

looks cool wonder where one can get it

I'd definitely place the Pyramid like ships as Stargate, very reminiscent of Ra's ship in the original movie.

I'd be interested in this mod if anyone found out what it was.

strange what is that ship above the tec refinery ship and what building is that below the same refinery ship?

Maybe they're just enlarged planetary elevators?  There are a number of different types, depending on the planet and race you're playing as, IIRC.  The little 'cars' that zip between them all are normally flat sprites based on trade/refinery frigates and capital ships.  Just some small details you might not normally notice.  I can't be entirely sure that the pyrimids are indeed planetary elevators though.  They may just be a mod object.