Search the forums for ‘brick’. This will find a number of threads that describe how to correctly partition a drive to make it work as a MyCloud. I can’t remember the best thread at the moment…
http://community.wd.com/t5/WD-My-Cloud/GUIDE-How-To-Unbrick-your-2TB-3TB-4TB-My-Cloud/td-p/765959
http://community.wd.com/t5/WD-My-Cloud/How-to-unbrick-a-totally-dead-WD-My-Cloud/td-p/631217/page/5
As for getting an image, I would suggest you do that my downloading the firmware image from the WD website, and then using zip to extract the rootfs.img file.
