In the current version, the logo can be user uploaded.
However, this means that the app has to handle user uploaded documents and serve them.

When building the admin for business client, the logo will most likely be in static files, and I think it could save some complexity to have the possibility to use a CharField that would point to a static file app/logo.png for example.

Then the template would be with a condition

{% if theme.use_static_logo %}}
    ...
    {% static theme.static_logo_path %}}
 {% else %}
     # The current behaviour
 {% endif %}

Wdyt ?