You can install the add-on Products.ContentWellPortlets and replace the top-viewlets with portlets, by adding a portlets.xml in one of your add-on's profiles.
This example adds a logo and an image next to it:
<?xml version ="1.0"?>
<portlets>
<!-- Assign Logo-portlet to site-root (key='/'): -->
<assignment name="top" category="context" key="/"
manager="ContentWellPortlets.InHeaderPortletManager1"
type="plone.portlet.static.Static" visible="True">
<!--
Give this portlet a name, so we can recognize it easily in the
portlet-management-UI via `[PLONESITE_URL]/manage-portletsinheader`:
-->
<property name="header">Logo</property>
<!-- But don't show its header and footer when viewing the portlet: -->
<property name="omit_border">True</property>
<!-- Replace 'Plone' with your site-id here, in case it differs: -->
<property name="text">
<a href="/Plone">
<img src="logo.png" />
</a>
</property>
</assignment>
<!-- Assign another portlet in next column (InHeaderPortletManager2): -->
<assignment name="top" category="context" key="/"
manager="ContentWellPortlets.InHeaderPortletManager2"
type="plone.portlet.static.Static" visible="True">
<property name="header">Some image next to Logo</property>
<property name="omit_border">True</property>
<property name="text">
<img src="defaultUser.png"
title="Dummy-user-avatar" />
</property>
</assignment>
</portlets>
And polish it with some styling.
For the search-box I'd may assign a search-portlet above the content (using ContentWellPortlets), give it a minus-margin-top and for the globnav a margin-right, but as there's many ways to Rome, I'd might replace the globnav with a navigation-portlet, too.
Here's an add-on for illustration-purposes (see its viewlets.xml on how to hide the top-viewlets):https://github.com/ida/adi/tree/master/adi.samplestructure