I think what blizzardjesus said was pretty apt, that this could be a game based in the heritage of Disney's traditional animation, wherein the abandonment has allowed corruption to creep in and threaten the citizens. In one of the concepts the sky clearly looks like the "sun" is coming through the raised corner of a box of some sort. I see it as an Imagineer's forgotten tool chest of traditional design tools. Paint thinner, brushes, pencils, and armature for sculptures, architecture from the Disney theme parks, etc. We've seen all of that so far, and I see a world in which all of that material and history is coming to life and trying to fight for survival. If that's the direction they're going, and that's how I interpret the Beach Attack concept art, then I am truly thrilled.
Yes, to address Odyssey's concerns, some of the character designs do seem a little bit sophomoric, but as others have said, I believe they were trying to push the limits of what Disney would allow done with their IP. That's the role of concept art when you're working with somebody else's IP, you have to find the limits of the freedom you've been given. Once they've done that, they can go back in during the (much more extensive) modeling stage and temper the initial creations with better taste and judgment. So it is foolhardy at best to dismiss the game out of hand because of a few pieces of art.
