Are you sure you used the correct dimensions for the image? The correct dimensions are 207x116. It was mentioned in the tutorial.
The problem may also be that you didn't mention in your SkinInfo in which folder you put the image. If you put the image in the folder "images" for example, then your code in the SkinInfo should look like this.
code:
<New>
<Pictures>
<Picture Id="59000"><File>images/59000.png</File></Picture>
</Pictures>
</New>