Maybe a flashy poster of all the factions in a fur ball with a purdy background, a usual custom of CE's is an art book, to show off the designs of the ships and characters, the pdf manual that comes in the game files maybe? softback and in color with maybe a little more lore. And a code that unlocks a set of unique flashy Symbols, profile pictures and maybe colour affects for the ICO online profile.
In my opinion that sounds like a pretty solid collectors edition, is the kind of thing that is on a large spread of different collector editions out there, and apart from the art book it doesn't sound like too much of a costly task, collectors edition wise.