I'm messing around with Embeddables. The following configuration does not give me the ability to upload an image...it just lets me insert a URL:
Should this work?
<propertyGroup id="options" labelText="Options">
<property id="backgroundImage" labelText="Image" dataType="url" controlType="Telligent.Evolution.Controls.UserFileUrlControl, Telligent.Evolution.Platform" validExtensions="gif,jpg,jpeg,png"/>
</propertyGroup>