Check out the 3D animation I did for the Doritos Crash the Superbowl contest. You make a 30 second commercial and Doritos is going to pick one to show during the superbowl. Watch it and then leave comments here (or better yet their site!).
Spartan, lifeless, dirty gray floor and background. Really ugly-looking gray rat/mouse---think about the kids in the audience. Then again, why a rodent? I know, it's obvious---cheese, therefor the rodent. I suggest creativity you must harness---choice/design of character and background, story, etc. Wrong I may be, but I have a strong feeling that you are not the only one with a rat/mouse entry. But if rodent you must, then rodent extraordinariness you must make it.