The article focuses on the key aspects of getting striking images and remarkable content right at the top of your page. The key is to make your impact in the first couple of seconds so that users will give you the thumbs up and continue to read your article.
In my experience (gained from watching other people Stumble) the most important issue is actually much more fundamental. You need to make sure your page loads quickly.
A large number of pages on StumbleUpon fail to load within the critical 3 second time limit before most people click for the next site. Some try to load external banner adverts, blog widgets, Java applets or large Flash files which slow the page down considerably.
If you want to maximise your StumbleUpon traffic invest in quick hosting and take the basic steps required to make your page load quickly.