I looked and looked for a Fedora 21 release of the wallpaper changer, Variety. I found a couple of prebuilt Fedora 20 RPMs but nothing for 21. What I did find was a SRPM. Honestly, I had no idea what to do with a SRPM. This is where my friend Google came into play. I found out how to build the SRPM and ended up with a working RPM of Variety.
You can download the Variety RPM from my Google Drive.