You need to set the Picture property, so...

Code:

$myPicture = "c:\winnt\sysvol\adioph\superman.bmp"

$PictureBox1.Picture = $myPicture

I'm not a real big fan of hard-coding paths. I'd rather see something like...

$myPicture = "%WINDIR%\sysvol\adioph\superman.bmp"