Two Ideas:

1. Remember that most of those Google image search results are another person's property, and not able to be used for commercial products and marketing without consent ($$$).

2. SOW looks so good already that the cover could be done with the game engine, and a little bit of photoshop to make if fit better, get rid of some of the jaggies.

Personally I think that would be a pretty nice advert, "Our game is so beautiful, we put the screen caps on the cover!"