http://shsforums.net and http://forums.gibberlings3.net are some examples of forums where a lot of work has gone into the styling. These are Invision Power Boards though and cost upwards of 150 dollars for a license. The features though are great. The SHS one is quite a bit busier but it’s still easy to find your way around I think. The Gibberlings3 one was something I did (and host/maintain) and is more minimalistic as it’s geared more towards programmers who don’t like a lot of glaring graphics.
I’ve seen some awesome skins for SMF forums but honestly if you’re going to do an active board that is used a lot, might be worth it to check into some of the non-free options.