Well, both skins we have now have these icons at a bit more than 25x25. I'd want to make these icons smaller, but the N graphics don't like to be shrunk, so 50x50 seemed like the smallest possible size. I don't think they're intolerably large.
To answer Brainwasher's question, the replied icon stays with a thread even if new posts arrive in the thread. So if you reply in a thread, then someone else posts, and you haven't read that post, that's where those Unread-Replied icons come in.
Anyway, Forum Buttons v2:
First, I fixed the un-rounded Read icons. I also made the drones look more like mailboxes, since you guys seemed to like that idea, and I changed the reply icons to have a gold border instead of an added gold piece, which I couldn't really fit anywhere. What do you think?