This is a pretty simple prank and it can be done with out code, but I think code gives it that extra gusto. The way this prank works is when you loud word it will set all active documents to have your own custom picture as the background. The guy to this is the picture.
For this example I used my avatar. I use it every where from Digg to IM:

I placed the picture in my c drive and copied the path. The key to this is that you want to be caught. I would recommend using an image of you giving a thumbs up or the middle finger. Something that says, I got you now. Once the picture is in follow these steps:
Step1: Open Word
Step2: Press Alt F11
Step3: Place code in your normal template
Sub autoexec()
Call prank
End SubSub prank()
Dim x As Document
Set x = ActiveDocumentActiveDocument.ActiveWindow.View.Type = wdWebView
ActiveDocument.Background.Fill.UserPicture _
PictureFile:=”C:\h.png”
End Sub
Step4: Add the path to your image on the line where it says picturefile:=”
Step5: Press Ctrl S (save)
Step6: Close word and wait
Got farther than last time. Now it says Command not available because no document is open, but it says it as microsoft word is loading right before the document opens. Also, when code is highlighted in red in the VBA screen, does that mean it’s not going to work?