Thank you. It was figured out. I was going from a folder on an external hard drive. The computer read it when I changed it in System Preferences but wasn't quick enough to read it from the external. We put the folder on the internal drive and it picked it up.So problem solved. Thanks for the response.

First time user here. I have recently upgraded to a new iMac retina 27" iO7. Transferred all from an older iMac. I have changed my desktop image in System preferences as I have done many times before. Looks good but upon each startup it reverts to the default image. Am I missing something here ...