@luke you could build something like that yourself, change background to the image, set post preview to 0 in ACP, job done. This is closer to a Reskin than a new theme in the strictest sense.
This is still in early design i plan on editting the tpl soon toon. Also i did say i was using lavendar as a base
Also i will make the image use jpg with progressive scans so its easier on mobile devices @psychobunny