A very simple work around that would only require a theme component would be to keep all your polls in one category. Once you do that it is straight forward to add an override that will add a poll icon to the topic lists cause it will require no backend server changes.
Or maybe even simpler … tag all your poll topics with the poll tag, then you can use the tag icon component and give it a nice visual cue. Would also make it super simple to find all the polls.