Not too difficult. All you need to (if you don't like the above option,
which is a good one BTW) ...

1) Put a picture/image box on a hidden form. (no title bar on the form)
2) Load your picture into it.
3) Resize the form to that of the picture box.
4) Pick random X and Y from the desktop params. (Be sure and get the number
of PIXELS)
5) Move your form to that location and make it visible for X amount of time
before loading a new pics and moving it again.