they should be infertile if anything

I believe it's possible to quickly mod the game to give them a custom ship style, but you'd need to create the UFOs yourself if no one else has done so (which I don't think they have).

do you known if there is any way to make them use ufo's of the game? that would be awesome

http://s752.photobucket.com/user/Evil_Emperor_Proteus/media/Ethereal%20Ones.png.html
My headcanon for the Ethereals was that they were considered Cold, Logical and Unscrupulous by the other races, making them unpopular, although they were polite and diplomatic with races that they feared and who were projected to be able to resist them. They are smart and logical enough to know when to treat their subjects well to create genuine loyalty and when to crack the whip, believing mindless brutality on their own subjects and servants to be self-destructive. They are pretty harsh to their enemies, however.

It is very imposing, and considering there are few good pictures of the Uber Ethereal, I'm not surprised we used the same one. If you wouldn't mind checking, how do the stats for each of our factions compare? I'd like to know if we had similar ideas or if I have a different picture in my mind of how the Ethereals work.

I made the "Ethereal Ones" as a faction for my game(along with many others) within a few days of the game's release. I like how we used the exact same pictures. It's a pretty imposing picture of an Ethereal, isn't it? :D