Jason Thomas and Gerhard Brueckl have both blogged on the subject of storing images as text inside a Power BI dataset:
Since they wrote those posts, however, Power BI has added the ability to set the Data Category property on measures as well as columns in tables. This means it is now possible to have the output of a DAX measure displayed as an image in a Power BI report and this in turn opens up a lot of new possibilities – including the ability to work around the maximum size of a text value that can be loaded into Power BI (see my previous blog post for more details) and therefore work with larger images.
I don’t understand why they make this so complicated. I have a Grafana dashboard widget that I show in a Power BI dashboard and have it scaled way down so it fits in under 32K. I appreciate Chris’s answer but that’s a lot of work to show an image.