If this is a problem you are facing on LION that whenever you launch Adobe Photoshop Elements, last opened photograph is always opened with it. This is something which is not related to Adobe Photoshop Elements and some default settings in LION are causing this.
This must have been happening with other applications as well. Did you notice it? So you want to stop this then go to System Preferences -> General and uncheck "Restore windows when quitting and reopening apps"