yeah, that's really the only way. Stumbling the topics your website is about yourself will give you ideas on what kind of articles / content stumblers in your niche are interested in. Then make something new based on that. Takes some creativity and thinking outside the box, I guess. In my own experience: if your site fits stumbleupon, and is large enough, the traffic will increase incrementally. I've had stumbleupon as my largest referrer (other than google) for a few weeks now - because people keep stumbling new pages on my site (and old favorites still get traffic, though never the burst they started with).