How to preview single picture in Photostreams

I would like to use Photo Stream, with a single pic to create a screensaver. when i try i get so many sec of the pic and then a black screen as if its a second pic.  Dont want that.  just the one pic. what am i doing wrong.   I duplicated the pic and added that, and then it fades out to the same pic.  Works, but kind of annoying! thoughts