At WordPress.com, every time we launch a new theme, we launch a demo site to go with it.
As a Theme Wrangler, after spending weeks working on a new theme, we spend hours on its demo site.
We tend to create a theme with a defined user type (e.g. Photographers) and as a result, the demo site targets that specific audience.
That being said, when we create a theme we think about all our users. We might have a specific use case in mind but we can’t always guess what the theme will be used for.
In fact, we are often surprised by our users, and what they can come up with and that’s why we try to make our themes as flexible as we can to accommodate their needs.

At WordPress.com, we have a great selection of themes that you can “Try & Customize” before activating it.
So if I could give you one piece of advice, go play with our themes and the customizer, and make it your site.