the easiest way to add things to stumbleupon is to download their toolbar for your browser. it has a "I like it!" button. you can submit any page, your etsy shop home, individual items, blog posts, a picture of your cat, go for it!
(when you click "I like it!" the page is submitted to your favorites. if the page has never been submitted to Stumbleupon before it comes up with another page where you can either 'quick submit' where they figure out all the categories for you or the other option is you can fill out a review and add the tags on your own.)