Featured Image for Structure Theme (Home, Top Left)

I don’t want an image in the header. The header for our blog should remain a text-only header.

Here is the way the front page of our blog appears now.
http://www.bachcroftblog.com/

As you can see, the “featured image” that should appear and be replaceable with each new post in a specific “Category” isn’t showing up. That’s the problem, and I’m looking for a solution.

We want a “magazine look,” so we want a new large “featured image” to appear when we post (under a specific catagory) once a month (sort of like publishing a new issue each month with a new cover). Our large “featured image” is supposed to appear on the left (next to the text widget on the right), under the title for the post. It doesn’t.

I’m using “Structure Theme” by Organic Themes. I simply want the theme to do what the theme’s description says it will do–display the “featured image” that I upload in the edit post screen. It worked the first time I added a post to the blog (but I deleted it, thinking something was wrong because, originally, I didn’t want the thumbnail in the post to have the exact same image as the one appearing in the “featured image” screen, but that’s not an issue anymore). Now, I can’t get a “Featured Image” to appear at all, no matter what I do.

As you can see, the space for the image is created, but the image doesn’t appear. Can you please tell me what to do?

We were thinking we’d buy the premium version for our web site, but not if we can’t even get the simple blog version to work.