That's a beautiful picture! Wish I had your skill...
I'll start by saying that I think there is a multiclassing option called "Brawler" (barbarian/soldier multiclass) in one of the "Hyborias FFF" books. There are probably also a bunch of feats that could be useful to you scattered around in a number of the various sourcebooks. I don't use any of the crunch other than that in the core rulebook, though, so I don't really know that stuff. So keep in mind that this is advice from a guy who only uses the core book.
First of all, what are your stats? You will definitely want a high Strength score, but if you're set on being a barbarian you'll also need a high Dexterity (since the barbarians best defense is Dex-based dodge).
Second, are you absolutely set on being a barbarian? I think it's a good choice, but you could also build a pitfighter-type with the soldier class.
Feats. Well, as a 6th level Nemedian barbarian you'll get five feats (regular feats a levels 1, 3 and 6, and racial bonus feats at levels 1 and 5). I think Improved Unarmed, Dodge and Brawl is a good start. Some people will say that Brawl is a pointless feat since you can strap on a gauntlet (as your character clearly has in the picture!) and get the same effect and also a little armour piercing, but I still think it's a cool feat because it helps you when you're fighting completely naked (and what barbarian worth his salt doesn't want to fight completely naked? :wink: ).
I would also get Improved Grapple as it can be a quite useful feat if your group is ganging up on someone (you hold him, while your friends stick him to death). Improved Trip is also supposed to be a very good feat, although I haven't seen it used enough in play to really know.
What I would advice you against is specializing in unarmed combat 100%. It can be very useful to be good at fighting without a weapon, but in some situations it will simply not be all that effective (you'll have problems against opponents in armour, for example). Sometimes you will want to pick up that huge axe and go to town. It's therefore a good idea to get some more general feats that will always help you. Improved Initiative is useful, and Power Attack is a great choice for a warrior with high Str (and you can use it unarmed!).
If I got to pick five feats for this guy it would therefore probably be: Improved Unarmed, Improved Grapple, Brawl, Dodge and Power Attack.
Oh, and welcome to the forums!
