Emails are an absolutely awful thing to do because of the fact that there are many different mail clients(gmail, outlook, etc...) and they all run differently. I know from recent experience that outlook does not support background-image or the position styling at all. There is also a few clients that will rip any divs you have out for some reason! In short there is no solution that will run on all email clients because emails are the devil! I found this website helpful for testing my emails though. http://putsmail.com/
http://backgrounds.cm/ this could work for some situations though