I wish we had example sites that included a deeper use of common elements and others like:

-Video
-Forums/blogs added to site
-Social icons
-Using the header and footer sections (think I just learned that the footer section actually puts code in the bottom of the body section.
-More on flexbox
-More on effects
Others?

Some of the things you mention are already in RSD, Social Icons and Flexbox instructions. And as to the header and footer, they can be used in RSD. Just check under Settings.
As to forums, blogs and effects, there are so many different ones out there, that it will take a whole book to cover them all.
It can generaloly be said, that if you find something that you want to implement, you can do that. If this 'something' needs scripts or css, you can add that in the header or footer in the Settings panel.

There is a bunch of help articles listed in the top of this discussion: 'Getting started with RSD. Tips, tricks and more.', together with instructional videos created by CC and many of the users.