Does anyone have a way to display an unique image/icon for each topic?

We have the author image displaying, but on a topical forum - like chapters in a book, we need to show an image for each 'chapter' or 'topic', rather than the author's image for every chapter/topic.

Here's the authors image code:
<img src="http://www.activemodules.com/desktopmodules/activesocial/profilepic.ashx?PortalId=0&uid=[AUTHORID]&w=32&h=32" title="[AF:AUTHORNAME]" border="0" />

Maybe something like:
<img src="http://www.activemodules.com/desktopmodules/activesocial/profilepic.ashx?PortalId=0&uid=[TOPICID]&w=32&h=32" border="0" />