I'll share the idea with you, as I was proud of what we ended up with. The premise was a product of the entire group, with about 80% of the art direction at my discretion--fonts, colors, illustrations, etc. Our basic idea was to create an environmental awareness campaign for the fictional "National Environmental Council" with a series of ads. We based it on the "This Little Piggy" nursery rhyme and showed our pig poster boy doing all kinds of horrible environmentally-unsound things. The slogan was then, "Don't be a pig."
Here is an ad and a book cover that I created, and a billboard idea from another team member. The book would be used in public schools and/or sold at retail stores. We also created reuseable shopping bags, recycle bins, and apparel whose proceeds would help the NEC:
Whew! Glad that's over!