Maybe it's just because Metroid had a eerie feel, but I'd guess that's what you're shooting for in general. I'm not sure what the goal is, or the story or anything like that; but for some general art styles a few examples come to mind...
Some levels of Flashback seem appropriate...
...or Alien Infestation has some great industrial type levels...
...and the old xmen 2 had a ton of futuristic alien-like level art...
... but maybe you're trying to avoid pixel art? Pixel art is great if you don't have alot of resources to put into the art. Nobody expects details if you don't have resolution.
Something simple like Limbo might be the way to go. Probably best to twist it though since that style has become popular.