Do we really need post icons ? I have seen prefix do the job better.
You can have both IMO.
I only "need" three: The ones to show you have posted in the thread - the ones to show if it is a poll or not - and the ones to show that it is a closed one.
Sticky ones are in a different color so they need no special icon. Oh, the three above can be "solved" with different colors too. Hm, it seems, I don't need them too. :D