On our board, the latest posticon in a specific topic will be your default post icon in other topics.

The hack is quite small, and maybe not the most clean way. But this way you got a very easy interface for members to update their default post icon. And there is only one little place to hack.

files affected:
/scripts/addpost.inc.php

You need to set the topic_id for the topic that contains the default post icons. Suggestions, I'd love to hear them.