I did this for the guys over at Rabid squirrel as well a while back, missed the competition deadline though, but thought i'd show it over here if people hadn't seen it. All I had was one of the outlines, the rest came as I went along
some nice work here dude just two quick suggestions. try a lil less saturation (bumblebee is like wow glowing ) second is that although there are shadows imo the some of the images look kinda flat. on the background i personally use two layers of shadow with the first set at 35% and the second at 55%. whilst with the characters etc i usally have both set at 45%. you have got some awsome work here though. just needs imo a lil more omph to really make it come alive