Great question. Yes, as a paid member you have much flexibility with your website theme and posts. By all means, photos and images make a site more inviting and are really necessary.

WordPress is the vehicle by which you add media for your pages and posts. Your theme determines the header options you have with images and menus.

As a paid member you can chose a different theme. There are 1000s to choose from. This is not addressed in Level 1 because Free Starter members do not have that option.

We use a free theme, Astra. When using a free theme it is important to note what design features you have available. If you find one you like you can take a look at it in action by going its developer site. When you choose a theme not its ratings and usage. Some free themes have very high usage which means that the developers will very likely keep supporting it. Even if you choose a theme now and change later that is OK because you do not loose your content posts and pages. You will have to make changes to your header and probably menu, but those are minor changes.

By going to the developers site for you chosen theme you will find documentation and videos of how to set things. up. Many times there are also YouTube videos available.

Adding images and color make your website uniquely yours.

Its really fun to do the decorating part.
If you need free images one place we use a lot is bing.com/images on upper right look for filter; click on it then see license in top center. Choose "use and share commercially."