First, we can't see your image and text in the question. But the easiest way to accomplish this, is to add a HTML panel to the bottom of your dashboard.
In the HTML panel, you can add text and a link to the image. This page in the documentation has an example, but it is the next-to-last example, so scroll down for a bit!
Dashboard Examples
Once you build this dashboard panel, you can save it and then refer to it in many dashboards. I strongly suggest that you put the image in a Splunk app, so that it is local to Splunk. For an example of this (along with another HTML panel example), take a look at this answers post:
Add Picture to Dashboard
