This is interesting... OS X remembers monitors you used with the machine and associates it with a wallpaper. I have one Mac mini, and two of everything else (two LCDs, two mice, two keyboards). The cheapo ones are at uni, while the nice ones are at home Anyway, during the summer when I was home, I had a Serenity wallpaper on. Then I went to uni, and sometime during the semester I changed the wallpaper to something else. Then when I came back home and hooked the Mac mini up to the LCD here, it switched back to the Serenity wallpaper! Interesting.