The crucial stage of this whole process is the distortion of the picture. Here's what you do.
Take your screenshot, add a border, mess around with it,whatever. When you are finished you have a nice picture with a size, in pixels, of say 160x64. But it could be whatever you like.
Now, distort the picture to 128x64 and save it. This is the file that goes in your mission folder. As you will know from reading fishion's tute it is essential that the file has sides a factor of 2: 32,64,128, 256 etc.
However, in your Overview you can define the size as it appears on the screen to be anything you like. So have
<p align="center"><img src="destroy.jpg" width="160" height="64">
to restore the picture to its original shape.
If all else fails, get hold of the
Tutorial Mission and use the Overview in there. Simply delete the pic and replace it with your own, which has the same name. That way you don't have to edit the code in the Overview at all. (Change the text obviously!)