Hi Ben,
Check the location of eo_web.ashx. We use eo_web.ashx to render the image files, and if access is denied on that file, the image file won't get rendered. For example, if you have:
Code: HTML/ASPX
<authorization>
<deny users="?"/>
</authorization>
You definitely want to add a "location" segment to spare eo_web.ashx, so that eo_web.ashx can be accessed by anonymous users.
Thanks