Certainly can. Follow these steps:
1. Go to Graphene Options > Advanced > Action Hooks Widget Areas. Click on the header.php
link, which will list all the action hooks in the header.php file.
2. Tick the graphene_before_content-main
action hook and save the settings.
3. Go to WP Admin > Appearance > Widgets. Notice that a new widget area has been added, called “Graphene Before Content-main”.
4. Add a text widget to this widget area, and add whatever HTML codes inside that text widget to display the banner.