Hm... Perhaps more in the way of 'space terrain'. It would be something that could restrict movement. Hey, what about all those scientific reports of 'dark matter'? I guess it would be awkward if you say its impassable, and then they discover what it really is.
Now that is unfortunate, imagine if you gave it certain properties, and then the scientists discovered its a time warping micro universes compressed?
Oh and more shapely babe aliens would be nice... mermaids, centaurettes, batwinged types with forked tails and maybe even ones with thick forearm hair...