Did you upload your image to the same directory?
The .png one that you altered from the one he provided?
As for myself, I have it working, I can't figure out how to put it in my sig yet.
I had to manually turn on in administration, configuration: class, href, a, img, border, and target.
Then I had to use this code to get it to work:
/a href = "http://www.contboard.com
" target = "_blank" class = "postlink" //img src = "http://www.contboard.com/signature.php
" border = 0///a/
replace the "/" in each case with a greater than or less than symbol, as appropriate.