Server resource usage not even above 10% on CPU or memory. As for CDNing imagery, what imagery are you talking about is slow to load?
The server response time can reach 5000+ ms. Are you only handling one request at a time? No idea what your server setup is like but if your CPU/memory usage is that low you can definitely handle concurrents.
Most of the assets seem to be proxied though CloudFlare, which is cool, but the TTL is way too low (4 hours). That makes sense for pages but not for assets that haven't changed in what, 4 years? If I'm not hitting the cache it can take 2 or 3 seconds to load all the little corner gifs. (it's 2014, flat is in)
Might as well minify your js/css one day when you're bored. ~7000 lines can add up. Could concat the files too but SMF probably makes that hard, no idea.
Other than that the site is fine. You could always move blocking scripts out of the header but computers are fast these days.