When using multiple monitors, desktop icons only appear in the leftmost monitor (that has its top-left coordinates at 0x0). This should be configurable so that any of the monitors could be set as the starting point for the desktop. See relevant discussion at http://forum.xfce.org/viewtopic.php?id=5492
Hello Oona, there's ongoing discussion in https://bugzilla.xfce.org/show_bug.cgi?id=3746 about how/where desktop icons should be placed. As your bug is also about icons placement, I'm marking it as duplicate because solving bug 3746 will also have to take your request into account. Please follow this bug then, and provide more info if needed. Thanks *** This bug has been marked as a duplicate of bug 3746 ***