If you're confused about what makes a good cover you could read Jennifer Crusie's criteria for a good cover. That might help you make a decision if you don't know which cover you like best. Basically we're looking for a cover that calls to you across the room, and when you get closer makes you want to pick it up.
By the way - these are covers I mocked up myself last evening. The real ones will be much more professional looking.
So here you go:
Option A: The Bridge Cover
Option B: The Green Cover
Option C: The Running down the Stairs cover
So tell me, what do you think?