Is recently had the need to show a picture column in a SharePoint list as a Persona element as provided in the Office UI Fabric. Now if it came down to it, it was just enough to have an image with a border radius, and not all the other mumbo jumbo from Persona.

The result looks as follows:

The json to put in the column formatting pane:

{
    "$schema": "https://developer.microsoft.com/json-schemas/sp/column-formatting.schema.json",
    "elmType": "div",
    "children": [
        {
            "elmType": "img",
            "attributes": {
                "src": "@currentField"
            },
            "style": {
                "width": "100px",
                "border-radius": "50%"
            }
        }
    ]
}