Combine text and image in RH9

I am trying to create an effect similar to one in PowerPoint where you can use an image as a text box, so that the text appears "on top of" the image, like

I would like this "text box clone" to resize according to the width of the topic window regardless of the text length.

I would use these for either a heading style or for the header on a master page.

I tried using a background image as shading for a one-celled table, but can't get the background image to resize. I'm unable to find anything like this in Help, even when searching through Google.

Any suggestions are welcome.

Thanks,

Julie WB