In designer "admin/company setup" at the bottom is dialog to upload your company logo (or whatever graphic) you want to appear in your designer. You can get really creative with that, so it is a great feature.
However, you can also write your own html header instead of using the logo feature. But, you do that in admin/Configure Layout. There are four areas there now:
1) Header code for designer
2) Footer code for designer
3) Header code for catalog
4) Footer code for catalog
This new announcement by Alex is that the Headers and Footers for Catalog are now totally separate features for your html coding pleasure.
Therefore, if you know even fundamental html programming, or can hire someone, you can design quite a bit of sweetness into the designer and catalog to make it look, behave and feel the way you desire. You can even mix the company setup logo feature along with the html feature to achieve even more control. As you may know, the logo area can be moved to different areas in the designer using the Layout Builder in Configure Layout. Imagine the possibilities.
That Alex is something else!
