When images are used as Table of Contents icons and as list icons, the goal is the same: make a presentable tiny image with reasonably consistent presentation. However, the way they go about this is different, partly as an artifact of Table of Contents being pure HTML and lists being wikitext.

This is not a high priority because the UI does not readily expose a way to create a hub feature with an image instead of an icon (you can edit it after the fact of course), but it still should be addressed.