Excel BIP Template - How to create a dynamic image placeholder

Summary

Need instructions for creating a dynamic logo within a BIP template

Content

We have many RTFs with dynamic logos on them, but we are now building a similar template using an Excel BIP template.  So, in our RTP - our alt-text field for the logo placeholder contains the following:

  url:{concat('${OA_MEDIA}','/',LOGO_PATH)}

Now, we need the same thing in the Excel template.  I followed the exact same steps and populated the alt text for the image with that same string, but it is still not pulling in any image onto the generated Excel document.