It's hard to argue that Windows Phone 7 Series' Metro UI concept isn't utterly unique in the mobile world, but it was wasn't the only option Microsoft considered -- far from it, in fact. The company has published a bunch a design concepts it churned through on its wild, wacky journey to finalizing Metro as we know it today, and one thing's for certain: they'd clearly planned on simple, square lines, partially-obscured typography, and in-your-face colors pretty much from day one. After careful consideration of everything they've got here, we still think we like the production design best, but that's kind of besides the point -- why, pray tell, couldn't these have just been user-selectable themes?