In the past I have written this article about how to get or create images for your sidebars: https://www.blogsbyheather.com/2008/10/how-to-get-the-images-for-the-sidebars.html
However, for those Stampin' Up! demonstrators, Michelle Laycock (www.laycockdesigns.com) and Amy Celona (www.websbyamy.com/blog) create beautiful images/buttons to use for your sidebars!
Not a demonstrator? I'm sure you could still contact these ladies to create an image or banner for your personal blog (of course for a fee – but they do beautiful work)!
Happy blogging!