I don't know anything about wallpaper white boards but Avedesk lets you keep wdget like notes which youc an write reminders on. They stay on your desktop at all times and you can move them around. Check it out: http://www.avedesk.org/

Here is a picture showing the notes I mentioned: http://www.zive.sk/Files/Obrazky/TestCentrum/2006/shareware/avedesk/pic1.jpg