On wolf and bear skins:
"Such dresses are mentioned in some Sagas, without there being any supernatural qualities attached to them. For instance, in the Njála there is mention of a man i geitheðni, in goatskin dress. Much in the same way do we hear of Harold Harfagr having in his company a band of berserkir, who were all dressed in wolf-skins, ulfheðnir, and this expression, wolf-skin coated, is met with as a man's name. Thus in the Holmverja Saga, there is mention of a Björn, "son of Ulfheðin, wolfskin coat, son of Ulfhamr, wolf-shaped, son of Ulf, wolf, son of Ulfhamr, wolf-shaped, who could change forms."
But the most conclusive passage is in the Vatnsdæla Saga, and is as follows:--"Those berserkir who were called ulfheðnir, had got wolf-skins over their mail coats" (c. xvi.) In like manner the word berserkr, used of a man possessed of superhuman powers, and subject. to accesses of diabolical fury, was originally applied to one of those doughty champions who went about in bear-sarks, or habits made of bear-skin over their armour. I am well aware that Björn Halldorson's derivation of berserkr, bare of sark, or destitute of clothing, has been hitherto generally received, but Sveibjörn {p. 37} Egilsson, an indisputable authority, rejects this derivation as untenable, and substitutes for it that which I have adopted."
... from this site
http://www.sacred-texts.com/goth/bow/bow05.htm
Wolf is fine. The stock swordsman in the game always looked like a german berserk to me.
Also from that site:
"they gnawed at their shield rims, and are said to have sometimes bitten them through, and as they rushed into conflict they yelped as dogs or howled as wolves."
Suggesting they often used shields. And perhaps a cool victory flic would be a howl.
Personally, I think the sword is the most likely weapon to be used by a far ranging viking warrior, including one who "berserks". But, of course, wolf garb, a blonde beard, and a sword and shield give you... the stock swordsman. I had entertained making that unit the berserk and the berserk would then become the huskarl.
So for variety, if you're intent on remaking this unit, a one-hand axe (or two) is a good option.
Maybe give your Berserkir red hair for a bit of difference???
Maybe a sword in one hand and an axe in the other, so he looks like he's a real dedicated and versatile butcher??? You could include two attack.flc's.
Whatever you do, I'm sure some people will love combining your unit, the PTW berserker, and the stock swordsman into a multiunit warband. I don't intend to use multiunits for irregulars, but that would look cool.
Good luck.
BTW, if you want to expand the game a bit further, a less romantic, but more practical Viking unit might be a Hersir: the original, land-owning, warrior-chiefs who ventured across Europe for plunder and conquest from the 8th century, before the Jarls and Kings took over the game. They had that generic "Viking" look: conical hat, chain armor with long skirt, long-hafted axe with moderate head, and bound wood shield (basically looking like a Norman foot soldier with a round, rather than kite, shield).
I'd also love to see a Frankish warrior with throwing axe (the converted AoE unit is highly inaccurate, IMO).