I haven't had time to see why or when they did it, but Google is not only forcing template changes on Blogger users, they are putting in a file size restriction for images. So, the original images were too large of a file size to be used without compressing them. Sorry if you linked to one and it no longer works, just find it again and follow the new instructions.
Find the background you want, point at the picture, Click on the picture to open it in full size, then right click it and choose "Save Image As" and save it to your computer. You can then upload it as a background!
I apologize for any inconveniece Google has caused with using these backgrounds.
