1.you can do it by creating a simple widget with a property..in the html use the value of this property to populate img src..this is extension creation..
2. if you want to use text/image object, create text/image object with background for each url. add them as master visualization and use show hide container with a condition for each image.
3. you can try with simple table extension using enable raw html and under if else use whole img src string, something like If(Sales<20M,'<img src="url1">','<img src="url2">')
I am not aware of any other way
