Would be great if OfficeJS insertHtml method in Word can support z-index styles so that you can create images behind the text like this:
<p class=MsoNormal>
<span style='position:absolute;z-index:-1895823360; margin-left:14px;margin-top:7px;width:330px;height:376px'>
<img width=220 height=251 src="some image source" >
</span>SOME TEXT IN FRONT OF THE IMAGE
</p>