Way back before we even started work in earnest on the first issue, Genevieve and I wanted to create character designs for each of the three layers, basically...main characters in the Islands in the Sky storyline that we'd introduce as the comic developed. The idea was to give a male and female pair from each layer their own promotional poster. Each pair would exemplify the design aesthetics of their layer and be positioned on or around an airship or glider...also from their layer.
Each poster would be strong enough to stand on its own, however, by making each poster wide and short, you could "stack" the posters...putting Overworld on top, Central in the middle, and Coreworld on the bottom. Naturally, Kayli and Gordo would represent Central but we never got around to fleshing out the designs for the other two layers and it may be some time before the story even reaches the other layers or has a chance to introduce those characters.
Still, it's one of the promotional items that Genevieve and I still want to do so if ever the stars align so that we can commit more time to this project, well...we can hope. =)