I like the first prototype combined with Zephyr's sparklies!
I would like to see the argyle pattern stretch across the whole background. It fades at the sides where they would be most visible, yet is centered right underneath where the threads would be, blocking the luscious argyleness. Another issue with the fading/composition is that Riku and Sora look really awkward when facing down on the right sides - you see their bodies, but their heads are being swallowed by "darkness". Their legs fading out into a white cloud background would be pretty neat though. (Also, I'd prefer them both upright.)
All-in-all, some good brainstorming. Can't wait to see the completed skins!