Is it possible (atm) to override or better extend an existing element via plugin?

I want to override or extend the element “image” ("…administration/src/module/sw-cms/elements/image"). Is it possible at the moment? First I want to extend or override the …/config/sw-cms-el-config-image.html.twig template, so I created the file in my plugin (MyPlugin/src/Resources/app/administration/src/module/sw-cms/elements/image/config/), but with no effect.

{% block sw_cms_element_image_config %}
    test...
{% endblock %}