I recently flashed to SS 4.8 themed from Lithium Watermark'd theme. I did a full whipe then installed the rom. I had everything setup but for some reason my wallpaper would not change. I tried force stopping Launcher Pro, I even uninstalled it and reinstalled it to see if that would work. Finally the wallpaper randomly changed after trying over 20 times. I tried again to see if the problem was resolved, and it wasn't ... I was just stuck with a new wallpaper.
Upon a phone reboot it works now. Don't know what it was or why a reboot fixed it. Just a heads up if anyone else has this issue.