I use Cargo rather than SMW. I was going to ask whether you are planning to change this extension to work with Cargo also. Then I saw your comment below: "I'm considering changing the extension to use page properties (built into MediaWiki core) rather than Semantic MediaWiki to store the title icon information." Have you had an opportunity to make progress on this? Thanks.
Topic on Extension talk:Title Icon
I have not had a chance to work on it, but it is still my intention to do so.