At work I have dual monitors on one with a third monitor from a second system right next to the other two displays for a sort of pseudo triple monitor setup. I personally always just prefer a little variety and use three different pics on each. Got a closeup of Mars on one, a nighttime skyline shot of Chicago on another and a shot of a beach on Kauai on another. Sometimes I'll have sort of themes (beach shots, etc.) but lately it's just been a mix of stuff.