Magento 2. Add attribute (image) to Catalog Price Rule

Question

Is it possible to add additional (image with Image Uploader) attribute to the Catalog Price Rule? If it is, please, tell about it in details. Better with working code example.

What I have now

Now I have only field with image uploader, but it just shows spinner and nothing more.

Code example

        <field name="img">
            <argument name="data" xsi:type="array">
                <item name="config" xsi:type="array">
                    <item name="label" xsi:type="string" translate="true">Image</item>
                    <item name="dataType" xsi:type="string">string</item>
                    <item name="source" xsi:type="string">catalog_rule</item>
                    <item name="formElement" xsi:type="string">fileUploader</item>
                    <item name="elementTmpl" xsi:type="string">ui/form/element/uploader/uploader</item>
                    <item name="previewTmpl" xsi:type="string">Magento_Catalog/image-preview</item
                    <item name="uploaderConfig" xsi:type="array">
                    <item name="url" xsi:type="string">catalog_rule/promo_catalog/image</item>
                    </item>
                </item>
            </argument>
        </field>

[UPD]

I have no frontend/routes.xml in my module. module-catalog-rule also doesn't have it. I use DI to inject ModelCollectionFactory of this module, where I need it.