This may be of interest to some :- http://support.apple.com/kb/HT2807 I've just recently installed Mavericks, and after applying my own wallpapers (i downloaded them from interfacelift), when shutting down, i sometimes see a "ghost" image of the wallpapers on the grey background just before it shuts down, but after it logs off. Thus, i can't take a screenshot, buts its annoying.. It doesn't happen all the time, but when it does, its only with my own wallpapers, and not the default Maverick's ones. On the plus side, i have not had this problem on 10.8.x .. Anyone got any ideas ? Apple told me to visit an Apple Store as a 'possible' screen issue, but if it was hardware, why does it only happen intermittently with the same wallpaper(s) applied ? Anyone else having this issue since Mavericks install ? I always thought CRT's were the subject to this, not LCD displays.. I guess i was wrong.