1. Fetch the image data

2. render the qweb with fetched data

3. use it in qweb

<img class="media-object dp img-circle"
     t-att-src="'data:image/png;base64,'+widget.employee_data.image_1920"
     style="width: 100px;height:100px;"/>

Hi.

Please checkout the coding of this module available for free in odoo apps, which adds a hr dashboard, the employee image is shown in the dashboard, so you can check and see how the code is done: https://apps.odoo.com/apps/modules/13.0/hrms_dashboard/

Also for creating dashboard using the board module, see: How To Create a Dashboard In Odoo

Thanks